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WPAN: INTRODUCTION A WPAN (Wireless PAN) is a short-distance wireless network specifically designed to support portable and mobile computing devices such.

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Presentation on theme: "WPAN: INTRODUCTION A WPAN (Wireless PAN) is a short-distance wireless network specifically designed to support portable and mobile computing devices such."— Presentation transcript:


2 WPAN: INTRODUCTION A WPAN (Wireless PAN) is a short-distance wireless network specifically designed to support portable and mobile computing devices such as PCs, PDAs, wireless printers and storage devices, cell phones, pagers, set-top boxes, and a variety of consumer electronics equipment. Bluetooth is an example of a wireless PAN that allows devices within close proximity to join together in ad hoc wireless networks in order to exchange information. Many cell phones have two radio interfaces-one for the cellular network and one for PAN connections.

3 WPAN WPANs such as Bluetooth provide the bandwidth
and convenience to make data exchange practical for mobile devices such as palm computers. Bluetooth overcomes many of the complications of other mobile data systems such as cellular packet data systems... The reach of a PAN is typically a few meters.

4 WPAN A Bluetooth PAN is also called a piconet, and is composed of up to 8 active devices in a master-slave relationship (up to 255 devices can be connected in 'parked' mode). The first Bluetooth device in the piconet is the master, and all other devices are slaves that communicate with the master. A piconet typically has a range of 10 meters, although ranges of up to 100 meters can be reached under ideal circumstances.

5 WPAN A wireless PAN consists of a dynamic group of less than 255 devices that communicate within about a 33-foot range. Unlike with wireless LANs, only devices within this limited area typically participate in the network, and no online connection with external devices is defined. One device is selected to assume the role of the controller during wireless PAN initialization, and this controller device mediates communication within the WPAN.

6 WPAN The controller broadcasts a beacon that lets all devices synchronize with each other and allocates time slots for the devices. Each device attempts to join the wireless PAN by requesting a time slot from the controller. The controller authenticates the devices and assigns time slots for each device to transmit data. The data may be sent to the entire wireless PAN using the wireless PAN destination address, or it may be directed to a particular device.

7 WPAN The working group is defining different versions for devices that have different requirements. focuses on high-bandwidth (about 55M bit/sec), low-power MAC and physical layers, while deals with low-bandwidth (about 250K bit/sec), extra-low power MAC and physical layers.

8 WPAN: History WPAN: smaller area of coverage, ad hoc only topology, plug and play architecture, support of voice and data devices, and low-power consumption. BodyLAN (DARPA, mid-1990s): inexpensive WPAN with modest bandwidth that could connect personal devices within a range of about 5 feet. project initiated a WPAN group in 1997. In March 1998, the HomeRF group was formed In May 1998, a Bluetooth special group was formed In March 1999, was approved as a separate group to handle WPAN

9 IEEE WPAN Development of standards for short distance wireless networks used for networking of portable ad mobile computing devices. The original functional requirement was published in January 22, 1998, and specified devices with: Power management: low current consumption Range: meters Speed: kbps Small size: .5 cubic inches without antenna Low cost relative to target device Should allow overlap of multiple networks in the same area Networking support for a minimum of 16 devices

10 IEEE WPAN The initial activities in the WPAN group included HomeRF and Bluetooth group. HomeRF currently has its own website [HomeRFweb] IEEE WPAN has four task groups: Task group 1: based on Bluetooth. Defines PHY and MAC for wireless connectivity with fixed, portable, and moving devices within or entering a personal operating space. Task group 2: focused on coexistence of WPAN and WLANs. Task group 3: PHY and MAC layers for high-rate WPANs (higher than 20 Mbps) Task group 4: ultra-low complexity, ultra-low power consuming, ultra-low cost PHY and MAC layer for data rates of up to 200 kbps.

11 Bluetooth Idea Universal radio interface for ad-hoc wireless connectivity Interconnecting computer and peripherals, handheld devices, PDAs, cell phones – replacement of IrDA Embedded in other devices, goal: 5€/device (2002: 50€/USB Bluetooth) Short range (10 m), low power consumption, license-free 2.45 GHz ISM Voice and data transmission, approx. 1 Mbit/s gross data rate

12 Bluetooth One of the first modules (Ericsson).

13 History and hi-tech…

14 Bluetooth History 1994: Ericsson (Mattison/Haartsen), “MC-link” project Renaming of the project: Bluetooth according to Harald “Blåtand” Gormsen [son of Gorm], King of Denmark in the 10th century 1998: foundation of Bluetooth SIG, 1999: erection of a rune stone at Ericsson/Lund 2001: first consumer products for mass market, spec. version 1.1 released Special Interest Group Original founding members: Ericsson, Intel, IBM, Nokia, Toshiba Added promoters: 3Com, Agere (was: Lucent), Microsoft, Motorola > 2500 members Common specification and certification of products

15 …and the real stone Located in Jelling, Denmark,
erected by King Harald “Blåtand” in memory of his parents. The stone has three sides – one side showing a picture of Christ. Inscription: "Harald king executes these sepulchral monuments after Gorm, his father and Thyra, his mother. The Harald who won the whole of Denmark and Norway and turned the Danes to Christianity." This could be the “original” colors of the stone. Inscription: “auk tani karthi kristna” (and made the Danes Christians) Btw: Blåtand means “of dark complexion” (not having a blue tooth…)

16 Characteristics 2.4 GHz ISM band, 79 RF channels, 1 MHz carrier spacing Channel 0: 2402 MHz … channel 78: 2480 MHz G-FSK modulation, mW transmit power FHSS and TDD Frequency hopping with 1600 hops/s Hopping sequence in a pseudo random fashion, determined by a master Time division duplex for send/receive separation Voice link – SCO (Synchronous Connection Oriented) FEC (forward error correction), no retransmission, 64 kbit/s duplex, point-to-point, circuit switched Data link – ACL (Asynchronous ConnectionLess) Asynchronous, fast acknowledge, point-to-multipoint, up to kbit/s symmetric or 723.2/57.6 kbit/s asymmetric, packet switched Topology Overlapping piconets (stars) forming a scatternet

17 Bluetooth Protocol Stack
Radio Baseband Link Manager Control Host Controller Interface Logical Link Control and Adaptation Protocol (L2CAP) Audio TCS BIN SDP OBEX vCal/vCard IP NW apps. TCP/UDP BNEP RFCOMM (serial line interface) AT modem commands telephony apps. audio apps. mgmnt. apps. AT: attention sequence OBEX: object exchange TCS BIN: telephony control protocol specification – binary BNEP: Bluetooth network encapsulation protocol SDP: service discovery protocol RFCOMM: radio frequency comm. PPP

18 Frequency Selection During Data Transmission (TDMA/TDD)
fk 625 µs fk+1 fk+2 fk+3 fk+4 fk+5 fk+6 M t symmetric asymmetric asymmetric

19 Overall Frame Format of Bluetooth Packets
The 48 bit address unique to every Bluetooth device is used as the seed to derive the sequence for hopping frequencies of the devices. Four types of access codes: Type 1: identifies a “M” terminal and its piconet address Type 2: identifies a “S” identity used to page a specific “S”. Type 3: Fixed access code reserved for the inquiry process (will be explained) Type 4: dedicated access code reserved to identify specific set of devices such as fax machines, printers, or cell phones. Header: 18 bits repeated 3 times with a 1/3 FEC code access code packet header payload 72 54 0-2745 bits S address type flow ARQN SEQN HEC 3 4 1 8 preamble sync. (trailer) 64 (4) bits

20 Overall Frame Format of Bluetooth Packets
S-address allows addressing the 7 possible “S” terminals in a piconet The 4-bit packet type allows for 16 choices of different grade voice systems: 6 of this payload types are asynchronous connectionless (ACL), primarily used for packet data communication 3 of the payload types are synchronous connection oriented (SCO), primarily used for voice communications 1 a integrated voice (SCO) and data (ACL) packet 4 are control packets common for both SCO and ACL links access code packet header payload 72 54 0-2745 bits S address type flow ARQN SEQN HEC 3 4 1 8 preamble sync. (trailer) 64 (4) bits

21 Control Packets Four types:
ID: occupies half of a slot, and it carries the access code with no data or even a packet type code NULL: used for ACK signaling, and there is no ACK for it POLL: similar to the NULL, but is has an ACK NULL and POLL: have the access code and the header, and so they have packet type codes and status report bits “M” terminals use the POLL packet to find the “S” terminals in their coverage area. FHS (Frequency Hop Synchronization): carries all the information necessary to synchronize two devices in terms of access code and hopping timing. This packet is used in the inquiry and paging process explained later.

22 Polling-based Transmission
Polling-based TDD packet transmission 625µs slots, master polls slaves SCO (Synchronous Connection Oriented) – Voice Periodic single slot packet assignment, 64 kbit/s full-duplex, point-to-point ACL (Asynchronous ConnectionLess) – Data Variable packet size (1,3,5 slots), asymmetric bandwidth, point-to-multipoint f6 f0 f1 f7 f12 f13 f19 f18 SCO ACL f5 f21 f4 f20 f8 f9 f17 f14 MASTER SLAVE 1 SLAVE 2

23 Connection Management
In the beginning of the formation of a piconet, all devices are in SB mode, then one of the devices starts with an inquiry and becomes the “M” terminal. During the inquiry process, “M” registers all the SB terminals that then become “S” terminals. After the inquiry process, identification and timing of all “S” terminals is sent to “M” using FHS packets. The “M” terminal starts a connection with a PAGE message including its timing and ID to the “S” terminal. When the connection is established, the communication takes place, and at the end, the terminal can be sent back to SB, Hold, park or Sniff states. Standby: do nothing Inquiry: search for other devices Page: connect to a specific device Connected: participate in a piconet

24 Connection Management
Hold, Park and Sniff are power-saving modes. The Hold mode is used when connecting several piconets or managing a low-power device. In the Hold mode, data transfer restarts as soon as the unit is out of this mode. In the Sniff mode, a slave listens to the piconet at reduced and programmable intervals according to the applications needs. In the Park mode a device gives up its MAC address but remains synchronized with the piconet. A Parked device does not participate in the traffic but occasionally listens to the traffic of “M” to resynchronize and check on broadcast messages. Park: release AMA, get PMA Sniff: listen periodically, not each slot Hold: stop ACL, SCO still possible, possibly participate in another piconet

25 Interference Between Bluetooth and 802.11
The WLAN industry specified three levels of overlapping: Interference: multiple wireless networks are said to interfere with one another if colocation causes significant performance degradation Coexistence: multiple wireless networks are said to coexist if they can be colocated without significant impact on performance. It provides for the ability of one system to perform a task in a shared frequency band with other systems that may or may not be using the same rules for operation Interoperation: provides for an environment with multiple wireless systems to perform a given task using a single set of rules

26 Piconet P=Parked M=Master SB=Standby S=Slave
Collection of devices connected in an ad hoc fashion One unit acts as master and the others as slaves for the lifetime of the piconet Master determines hopping pattern, slaves have to synchronize Each piconet has a unique hopping pattern Participation in a piconet = synchronization to hopping sequence Each piconet has one master and up to 7 simultaneous slaves (> 200 could be parked) P S S M P SB S P SB M=Master S=Slave P=Parked SB=Standby

27 Forming a Piconet        
All devices in a piconet hop together Master gives slaves its clock and device ID Hopping pattern: determined by device ID (48 bit, unique worldwide) Phase in hopping pattern determined by clock Addressing Active Member Address (AMA, 3 bit) Parked Member Address (PMA, 8 bit) SB M S P

28 Scatternet Linking of multiple co-located piconets through the sharing of common master or slave devices Devices can be slave in one piconet and master of another Communication between piconets Devices jumping back and forth between the piconets M S P SB Piconets (each with a capacity of < 1 Mbit/s) M=Master S=Slave P=Parked SB=Standby

29 WPAN: IEEE 802.15-1 – Bluetooth
Data rate Synchronous, connection-oriented: 64 kbit/s Asynchronous, connectionless 433.9 kbit/s symmetric 723.2 / 57.6 kbit/s asymmetric Transmission range POS (Personal Operating Space) up to 10 m with special transceivers up to 100 m Frequency Free 2.4 GHz ISM-band Security Challenge/response (SAFER+), hopping sequence Cost 50€ adapter, drop to 5€ if integrated Availability Integrated into some products, several vendors Connection set-up time Depends on power-mode Max. 2.56s, avg. 0.64s Quality of Service Guarantees, ARQ/FEC Manageability Public/private keys needed, key management not specified, simple system integration Special Advantages/Disadvantages Advantage: already integrated into several products, available worldwide, free ISM-band, several vendors, simple system, simple ad-hoc networking, peer to peer, scatternets Disadvantage: interference on ISM-band, limited range, max. 8 devices/network&master, high set-up latency

30 WPAN: IEEE 802.15 – future developments 1
: Coexistence Coexistence of Wireless Personal Area Networks (802.15) and Wireless Local Area Networks (802.11), quantify the mutual interference : High-Rate Standard for high-rate (20Mbit/s or greater) WPANs, while still low-power/low-cost Data Rates: 11, 22, 33, 44, 55 Mbit/s Quality of Service isochronous protocol Ad hoc peer-to-peer networking Security Low power consumption Low cost Designed to meet the demanding requirements of portable consumer imaging and multimedia applications

31 WPAN: IEEE 802.15 – future developments 2
: Low-Rate, Very Low-Power Low data rate solution with multi-month to multi-year battery life and very low complexity Potential applications are sensors, interactive toys, smart badges, remote controls, and home automation Data rates of kbit/s, latency down to 15 ms Master-Slave or Peer-to-Peer operation Support for critical latency devices, such as joysticks CSMA/CA channel access (data centric), slotted (beacon) or unslotted Automatic network establishment by the PAN coordinator Dynamic device addressing, flexible addressing format Fully handshaked protocol for transfer reliability Power management to ensure low power consumption 16 channels in the 2.4 GHz ISM band, 10 channels in the 915 MHz US ISM band and one channel in the European 868 MHz band

32 Why not use Wireless LANs?
Bluetooth Why not use Wireless LANs? - power - cost A cable replacement technology 1 Mb/s symbol rate Range 10+ meters Single chip radio + baseband at low power & low price point ($5)

33 IEEE 802.11: Classical WLANs Replacement for Ethernet
Supported data rates 11, 5.5, 2, 1 Mbps; and recently up to 2.4 GHz up to 54 Mbps in 5.7 GHz band ( a) Range Indoor meters Outdoor: 50 – 100 meters Transmit power up to 100 mW Cost: Chipsets $ 35 – 50 AP $200 - $1000 PCMCIA cards $100 - $150

34 blurring the distinction
Emerging Landscape IEEE Bluetooth 802.11b for PDAs Bluetooth for LAN access New developments are blurring the distinction Cordless headset LAN AP Which option is technically superior ? What market forces are at play ? What can be said about the future ?

35 Bluetooth Working Group History
February 1998: The Bluetooth SIG is formed promoter company group: Ericsson, IBM, Intel, Nokia, Toshiba May 1998: Public announcement of the Bluetooth SIG July 1999: 1.0A spec (>1,500 pages) is published December 1999: ver. 1.0B is released December 1999: The promoter group increases to 9 3Com, Lucent, Microsoft, Motorola March 2001: ver. 1.1 is released Aug 2001: There are 2,491+ adopter companies

36 New Applications

37 Synchronization User benefits
Automatic synchronization of calendars, address books, business cards Push button synchronization Proximity operation

38 Cordless Headset User benefits Multiple device access
Cordless phone benefits Hands free operation

39 Usage Scenarios Examples
Data Access Points Synchronization Headset Conference Table Cordless Computer Business Card Exchange Instant Postcard Computer Speakerphone

40 Bluetooth Specifications

41 Bluetooth Specifications
Applications HCI IP SDP RFCOMM Data Audio L2CAP Single chip with RS-232, USB, or PC card interface Link Manager Baseband RF A hardware/software/protocol description An application framework

42 Interoperability & Profiles
Applications Represents default solution for a usage model Vertical slice through the protocol stack Basis for interoperability and logo requirements Each Bluetooth device supports one or more profiles Protocols Profiles

43 Bluetooth Profiles (in version 1.2 release)
Generic Access Service Discovery Cordless Telephone Intercom Serial Port Headset Dial-up Networking Fax LAN Access Generic Object Exchange Object Push File Transfer Synchronization

44 Technical Overview

45 Bluetooth Radio Specification
RF Baseband Audio Link Manager L2CAP Data Control SDP RFCOMM IP Applications

46 Design considerations
Noise, interference power spectrum Data signal x(t) Recovered data signal cost Goal high bandwidth conserve battery power cost < $10

47 EM Spectrum    ISM band
902 – 928 Mhz 2.4 – Ghz 5.725 – Ghz ISM band AM radio S/W radio FM radio TV TV cellular LF HF VHF UHF SHF EHF MF 30kHz 300kHz 3MHz 30MHz 300MHz 30GHz 300GHz 10km 1km 100m 10m 1m 10cm 1cm 100mm 3GHz X rays Gamma rays infrared visible UV 1 kHz 1 MHz 1 GHz 1 THz 1 PHz 1 EHz Propagation characteristics are different in each frequency band

48 Unlicensed Radio Spectrum
33cm 12cm 5cm 26 Mhz 83.5 Mhz 125 Mhz 902 Mhz 2.4 Ghz 5.725 Ghz 928 Mhz Ghz 5.785 Ghz cordless phones baby monitors Wireless LANs 802.11 Bluetooth Microwave oven 802.11a HyperLan

49 Bluetooth Radio Link frequency hopping spread spectrum
1Mhz . . . 1 2 3 79 83.5 Mhz frequency hopping spread spectrum 2.402 GHz + k MHz, k=0, …, 78 1,600 hops per second GFSK modulation 1 Mb/s symbol rate transmit power 0 dbm (up to 20dbm with power control)

50 Review of Basic Concepts

51 Baseband Applications Control Applications Data Control Data Baseband
IP SDP RFCOMM RF Baseband Audio Link Manager L2CAP Data Control SDP RFCOMM IP Applications Data Audio L2CAP Link Manager Baseband RF

52 Bluetooth Physical Link
Point to point link master - slave relationship radios can function as masters or slaves m s s m Piconet Master can connect to 7 slaves Each piconet has max capacity =1 Mbps hopping pattern is determined by the master

53 Connection Setup Inquiry - scan protocol
to learn about the clock offset and device address of other nodes in proximity

54 Inquiry on Time Axis f1 f2 Slave1 Inquiry hopping sequence Master

55 Piconet Formation Page - scan protocol
Master Active Slave Parked Slave Standby Page - scan protocol to establish links with nodes in proximity

56 Addressing Bluetooth device address (BD_ADDR)
48 bit IEEE MAC address Active Member address (AM_ADDR) 3 bits active slave address all zero broadcast address Parked Member address (PM_ADDR) 8 bit parked slave address

57 Piconet Channel m s1 s2 FH/TDD f1 f2 f3 f4 f5 f6 625 sec
1600 hops/sec

58 Multi Slot Packets m s1 s2 Data rate depends on type of packet FH/TDD
625 µsec Data rate depends on type of packet

59 Physical Link Types Asynchronous Connection-less (ACL) Link
Synchronous Connection Oriented (SCO) Link slot reservation at fixed intervals Asynchronous Connection-less (ACL) Link Polling access method SCO SCO ACL ACL m If there is no data to be sent on the ACL link and no polling is required, no transmission shall take place. If a slave fails to decode the slave address in the packet header, it is not allowed to transmit in the next slot. However, on an SCO link, the slave can go ahead and transmit in its allocated slot even if the decoding fails in the preceding slot. SCO slave shall not transmit in its allocated slot if a different slave was addressed in the previous master-to-slave slot. A collision can happen when a slave incorrectly decodes a packet addressed to another slave and responds s1 s2

60 Packet Types Data/voice Control packets packets Voice data ID* Null
Poll FHS DM1 HV1 HV2 HV3 DV DM1 DM3 DM5 DH1 DH3 DH5 Add channel mapping discussion here: Link Control Channel (packet header) Link Management channel L2CAP SCO

61 Packet Format 72 bits 54 bits 0 - 2744 bits Access code Header Payload
Voice header Data CRC No CRC No retries ARQ FEC (optional) FEC (optional) Mention that over SCO link you cannot carry any other real-time traffic. There is no protocol-id field in the SCO header/payload. Is this really true? 625 µs master slave

62 Access Code Synchronization DC offset compensation Identification
72 bits Access code Header Payload Channel Access Code (CAC) Device Access Code (DAC) Inquiry Access Code (IAC) Types Purpose Synchronization DC offset compensation Identification Signaling X

63 Packet Header m s Purpose Max 7 active slaves Addressing (3)
54 bits s m Access code Header Payload Purpose Max 7 active slaves Addressing (3) Packet type (4) Flow control (1) 1-bit ARQ (1) Sequencing (1) HEC (8) 16 packet types (some unused) Broadcast packets are not ACKed How useful is header protection when payload is unprotected For filtering retransmitted packets Verify header integrity total 18 bits Encode with 1/3 FEC to get 54 bits

64 Voice Packets (HV1, HV2, HV3)
72 bits 54 bits 240 bits = 366 bits Access code Header 30 bytes Payload HV1 10 bytes + 1/3 FEC HV2 20 bytes + 2/3 FEC HV3 30 bytes 3.75ms (HV3) 2.5ms (HV2) 1.25ms (HV1)

65 Data Packet Types DM1 DM3 DM5 2/3 FEC No FEC DH1 DH3 DH5

66 Inter Piconet Communication
Cordless headset Cell phone mouse Cordless headset Cell phone Cell phone Cordless headset

67 Scatternet

68 Scatternet, Scenario 2 How to schedule presence in two piconets?
Forwarding delay ? Missed traffic?

69 Baseband: Summary TDD, frequency hopping physical layer
L2CAP LMP Physical Data link Device 2 Device 1 TDD, frequency hopping physical layer Device inquiry and paging Two types of links: SCO and ACL links Multiple packet types (multiple data rates with and without FEC)

70 Link Manager Protocol Applications Control Data Setup and management
RF Baseband Audio Link Manager L2CAP Data Control SDP RFCOMM IP Applications Setup and management of Baseband connections Piconet Management Link Configuration Security LMP

71 Piconet Management m s Attach and detach slaves Master-slave switch
Establishing SCO links Handling of low power modes ( Sniff, Hold, Park) Paging s m req Master Slave response

72 Low Power Mode (hold) Hold offset Slave Hold duration Master

73 Low Power Mode (Sniff) Traffic reduced to periodic sniff slots
Sniff offset Sniff duration Slave Sniff period Master Traffic reduced to periodic sniff slots

74 Low Power Mode (Park) Slave Beacon instant Master Beacon interval Power saving + keep more than 7 slaves in a piconet Give up active member address, yet maintain synchronization Communication via broadcast LMP messages

75 Connection Establishment & Security
Goals Authenticated access Only accept connections from trusted devices Privacy of communication prevent eavesdropping Paging LMP_host_conn_req LMP Accepted Constraints Processing and memory limitations $10 headsets, joysticks Cannot rely on PKI Simple user experience Security procedure Master Slave LMP_setup_complete LMP_setup_complete

76 Authentication Authentication is based on link key (128 bit shared secret between two devices) How can link keys be distributed securely ? challenge response Verifier Claimant accepted Link key Link key

77 Pairing (Key Distribution)
Pairing is a process of establishing a trusted secret channel between two devices (construction of initialization key Kinit) Kinit is then used to distribute unit keys or combination keys PIN + Claimant address PIN + Claimant address Verifier Claimant Random number challenge Random number response Random number accepted Kinit Kinit

78 Link Manager Protocol Summary
Baseband L2CAP LMP Physical Data link Device 2 Device 1 Piconet management Link configuration Low power modes QoS Packet type selection Security: authentication and encryption

79 Logical Link Control and
L2CAP Applications Logical Link Control and Adaptation Protocol IP SDP RFCOMM Data L2CAP provides Protocol multiplexing Segmentation and Re-assembly Quality of service negotiation Audio L2CAP Link Manager Baseband RF

80 Logical Link Control and
L2CAP Applications Logical Link Control and Adaptation Protocol IP SDP RFCOMM Data L2CAP provides Protocol multiplexing Segmentation and Re-assembly Quality of service negotiation Audio L2CAP Link Manager Baseband RF

81 Why baseband isn’t sufficient?
IP RFCOMM Multiplexing demultiplexing MTU Baseband provides hard coded choices for ARQ and FEC. How good those choices are in providing good quality of service. Would it be better to provide more flexibility to the higher layers? reliable*, flow controlled Baseband in-sequence, asynchronous link Baseband packet size is very small (17min, 339 max) No protocol-id field in the baseband header

82 Need a Multiprotocol Encapsulation Layer
RFCOMM IP RFCOMM unreliable, no integrity reliable*, in-order, flow controlled, ACL link Baseband provides hard coded choices for ARQ and FEC. How good those choices are in providing good quality of service. Would it be better to provide more flexibility to the higher layers? If we were to define another adaptation layer on top of SCO link, what would it look like? What problem you’ll run into if you try to use L2CAP segmentation/reassembly over multihop links? Ans: L2CAP fragments have no-id. It is impossible to distinguish one fragment from the other. What is the use of the flow-control bit in the ACL payload header? How is it different from the Flow bit in the baseband header? How about ARQ at L2CAP layer and no reliability at Baseband? What about Reliability? Connection oriented or connectionless? integrity checks? Desired features Protocol multiplexing Segmentation and re-assembly Quality of service

83 Segmentation and Reassembly
Length Payload Baseband packets CRC CRC CRC Min MTU = 48 equals two DH1 packets – 6 (l2cap header) = 48. Default MTU = 672 equals two DH5 packets – 6 = 672. Analyze how well links be utilized for different combinations of higher layer MTU, negotiated L2CAP MTU, and choice of packet types. start of L2CAP continuation of L2CAP continuation of L2CAP cannot cope with re-ordering or loss mixing of multiple L2CAP fragments not allowed If the start of L2CAP packet is not acked, the rest should be discarded min MTU = 48 672 default

84 Multiplexing and Demultiplexing
RFCOMM IP RFCOMM Circuit or connection-less ? Why is L2CAP connection oriented ? Baseband is polling based Bandwidth efficiency - carry state in each packet Vs. maintain it at end-points Need ability for logical link configuration MTU reliability (Flush timeout option) QoS (token bucket parameter negotiation) Evaluate design choices of L2CAP. Simplicity was one of the goals, but was it achieved? Parameter negotiation adds complexity and extra round trips. Since memory and processing are becoming cheap, it is not clear if the flexibility offered by parameter negotiation buys anything at all. MTU, reliability, and QoS should be link properties, not per L2CAP connection properties. I wonder how often different protocols will use different params for L2CAP connection.

85 L2CAP Channels Length CID Payload Slave #1 master Slave #3
signaling channel Slave #1 master 01 01 Slave #3 01 01 CID CID CID CID CID CID data channel CID 01 Signaling channel CID does not uniquely determine the identity of the source L2CAP entity Signaling channel for 1) connection establishment 2) channel configuration 3) disconnection CID 01 Slave #2

86 L2CAP Connection: an Example
Initiator Target L2CAP_ConnectReq Establishment L2CAP_ConnectRsp L2CAP_ConfigReq Configuration L2CAP_ConfigRsp MTU, QoS reliability L2CAP_ConfigReq L2CAP_ConfigRsp Data transfer L2CAP_DisconnectReq Termination L2CAP_DisconnectRsp

87 L2CAP Packet Format (Connectionless)
Length DCID Payload 2 2+ 0 – 64K PSM Not fully developed yet.

88 L2CAP: Summary Design constraints: Assumptions about the lower layer
Simplicity Low overhead Limited computation and memory Power efficient Assumptions about the lower layer Reliable, in-order delivery of fragments Integrity checks on each fragment Asynchronous, best effort point-to-point link No duplication Full duplex Food for thought: L2CAP header has no protection at all. Length field is the only protection. Which other protocol has similar header? Comment: - Protocol designed for a specific link - L2CAP over other media will not work! Service provided to the higher layer Protocol multiplexing and demultiplexing Larger MTU than baseband Point to point communication

89 Bluetooth Service Discovery Protocol
Applications IP SDP RFCOMM Data Audio L2CAP Link Manager Baseband RF

90 Example usage of SDP Establish L2CAP connection to remote device
Query for services search for specific class of service, or browse for services Retrieve attributes that detail how to connect to the service Establish a separate (non-SDP) connection to use the service

91 Serial Port Emulation using RFCOMM
Applications IP SDP RFCOMM Data Serial Port emulation on top of a packet oriented link Similar to HDLC For supporting legacy apps Audio L2CAP Link Manager Baseband RF

92 Serial Line Emulation over Packet based MAC
RFCOMM RFCOMM L2CAP L2CAP Design considerations framing: assemble bit stream into bytes and, subsequently, into packets transport: in-sequence, reliable delivery of serial stream control signals: RTS, CTS, DTR

93 IP over Bluetooth V 1.0 Applications GOALS Data
SDP RFCOMM GOALS Data Internet access using cell phones Connect PDA devices & laptop computers to the Internet via LAN access points Audio L2CAP Link Manager Baseband RF

94 LAN Access Point Profile
IP Access Point PPP Security Authentication Access control Efficiency header and data compression Auto-configuration Lower barrier for deployment Why use PPP? RFCOMM L2CAP Baseband

95 Inefficiency of Layering
Palmtop LAN access point IP IP packet oriented PPP PPP rfc 1662 byte oriented rfc 1662 RFCOMM RFCOMM packet oriented L2CAP L2CAP Emulation of RS-232 over the Bluetooth radio link could be eliminated

96 Terminate PPP at LAN Access Point
Palmtop Access Point IP IP PPP PPP ethernet RFCOMM RFCOMM Bluetooth Bluetooth PPP server function at each access point management of user name/password is an issue roaming is not seamless

97 L2TP Tunneling Palmtop Access Point PPP server IP IP PPP PPP ethernet IP UDP ethernet IP UDP RFCOMM RFCOMM Bluetooth Bluetooth Tunneling PPP traffic from access points to the PPP server 1) centralized management of user name/password 2) reduction of processing and state maintenance at each access point 3) seamless roaming

98 Seamless Roaming with PPP
REQ 1 Server CLR 5 RPL 4 REQ 3 RPL 2 AP1 AP2 MAC level handoff MAC level registration PPP PPP palmtop

99 IP over Bluetooth v 1.1: BNEP
Access Point IP Bluetooth Network Encapsulation Protocol (BNEP) provides emulation of Ethernet over L2CAP BNEP BNEP defines a frame format which includes IEEE 48 bit MAC addresses A method for encapsulating BNEP frames using L2CAP Option to compress header fields to conserve space Control messages to activate filtering of messages at Access Point L2CAP Baseband

100 Bluetooth Current Market Outlook

101 Market Forecasts for Year 2005
Cahners In-stat (2000 forcast) revised (2001 forcast) $ 5.4 bn Merrill Lynch (2000 forcast) revised (2001 forcast) $ 4.4 bn 2.1 bn $ 4.3 bn 1.4 bn $ 2.2 bn 1.5 bn $ 4.4 995 m $ 3.6 $ 2.02 Units sold annually Revenue Chip price

102 Bluetooth Value Chain Wireless Carriers Stack providers Software
Conspicuously missing Stack providers Software vendors Integrators Silicon Radio

103 Value to Carriers: Synchronization and Push
More bits over the air Utilization of unused capacity during non-busy periods Higher barrier for switching service providers

104 Value to Carriers: Cell phone as an IP Gateway
Will Pilot and cell phone eventually merge? More bits over the air Enhanced user experience Palmpilot has a better UI than a cell phone Growth into other vertical markets

105 Value to Carriers: Call Handoff
Cordless base Threat or opportunity? More attractive calling plans Alleviate system load during peak periods Serve more users with fewer resources

106 Biggest Challenges facing Bluetooth
Interoperability Always a challenge for any new technology Hyped up expectations Out of the box ease of use Cost target $5 Critical mass RF in silicon Conflicting interests – business and engineering

107 References [1] IEEE , “Wireless LAN MAC and Physical Layer Specification,” June 1997. [2] Hirt, W.; Hassner, M.; Heise, N. “IrDA–VFIr (16 Mb/s): modulation code and system design.” IEEE Personal Communications, vol.8, (no.1), IEEE, Feb [3] Lansford, J.; Bahl, P. “The design and implementation of HomeRF: a radio frequency wireless networking standard for the connected home.” Proceedings of the IEEE, IEEE, Oct [4] Specification of Bluetooth System, ver. 1.0, July 1999

108 References (cnt) [5] Haartsen, J.C. “The Bluetooth radio system.”, IEEE Personal Communications, IEEE, Feb [6] Haartsen, J.C. ‘Bluetooth towards ubiquitous wireless connectivity.’, Revue HF, Soc. Belge Ing. Telecommun. & Electron, p.8–16. [7] Rathi, S. “Bluetooth protocol architecture.” Dedicated Systems Magazine, Dedicated Systems Experts, Oct.–Dec [8] Haartsen, J.C.; Mattisson, S. “Bluetooth–a new low–power radio interface providing short–range connectivity.” Proceedings of the IEEE, IEEE, Oct [9] Gilb, J.P.K “Bluetooth radio architectures.” 2000 IEEE Radio Frequency Integrated Circuits (RFIC) Symposium Digest of Papers, Boston, MA, USA, 11–13 June 2000.

109 References (cnt) [10] N. Benvenuto, G. Cherubini, “Algoritmi e circuiti per le telecomunicazioni”, Ed. Libreria Progetto. [11] The Bluetooth Special Interest Group, Documentation available at [12] IEEE Working Group for WPANs™; [13] Barker, P.; Boucouvalas, A.C.; Vitsas, V. “Performance modelling of the IrDA infrared wireless communications protocol.” International Journal of Communication Systems, vol.13, Wiley, Nov.–Dec [14] Tokarz, K.; Zielinski, B. “Performance evaluation of IrDA wireless transmission.” 7th Conference on Computer Networks, Zakopane, Poland, 14–16 June 2000. [15] ETSI RES, “Digital European Cordless Telecommunications (DECT), Common interface Part 1: Overview,” ETS –1, 1996.

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