Transcript WPAN - Feng Xia

WPAN
IEEE 802.15.4 (ZigBee)
WWAN
< 15 km
802.20, GSM, GPRS, CDMA,
2.5G, 3G, 4G
WMAN
< 5 km
802.16 – 70 Mbps
LMDS – 38 Mbps
WLAN
< 150 m
11 – 54 Mbps
802.11
HiperLAN/2
WPAN
< 10 m
Bluetooth、UWB、
Zigbee
无线通信网络分类图
Common Aliases for Wireless Standards
802.11
Wi-Fi
802.15.1
Bluetooth
802.15.3
Ultra Wideband
802.15.4
ZigBee
802.16
WiMAX
IEEE 802.15 Working Group for
Wireless Personal Area Networks
• The 802.15 WPAN effort focuses on the
development of consensus standards for
Personal Area Networks (PAN) or short distance
wireless networks
• WPANs address wireless networking of portable
and mobile computing devices such as: PCs,
Personal Digital Assistants (PDAs), peripherals,
cell phones, pagers, and consumer electronics;
allowing these devices to communicate and
interoperate with one another.
Example of home equipment
demanding network operations
IEEE Project 802 Standards
WLAN
WPAN
WMAN
LR-WPAN
IEEE 802.15 Working Group
IEEE 802.15 Protocol Architecture
Wireless Local Networks
Bluetooth
• In 1998 – Ericsson, IBM, Toshiba, Nokia and Intel form
Bluetooth Special Interest Group (SIG).
• Harald Bluetooth – Danish king who lived more than 1000
years ago
•
•
•
•
•
Universal short-range wireless capability
Uses 2.4-GHz band
Available globally for unlicensed users
Devices within 10 m can share up to 720 kbps of capacity
Supports open-ended list of applications
– Data, audio, graphics, video
• Data rate – 1 Mbps
Bluetooth Applications
Landline
Cable
Replacement
Data/Voice
Access
Points
- Synchronization
- Cordless Headset
…and combinations!
Personal Ad-hoc
Networks
It is reported that more than two billion Bluetooth-ready devices were shipped
during 2012 – over 50 millions every day.
Radio Specification
• Classes of transmitters (on which Bluetooth products are
available):
– Class 1: Outputs 100 mW for maximum range
• Power control mandatory
• Provides greatest distance – up to 100 m
• Products: still available
– Class 2: Outputs 2.4 – 2.5 mW at maximum
• Power control optional
• Transmission distance – 10 m
• Products: most common
– Class 3: Nominal output is 1 mW
• Lowest power
• Transmission distance – 10 cm – 1 m
• Products - rare
Bluetooth Standards Documents
• Core specifications
– Details of various layers of Bluetooth protocol
architecture
• Profile specifications
– Use of Bluetooth technology to support various
applications
Bluetooth Protocol Stack
Bluetooth Protocol Stack
Composed of protocols to allow
Bluetooth devices to locate each
other and to create, configure
and manage both physical and
logical links that allow higher
layer protocols and applications
to pass data through these
transport protocols
Applications
IP
SDP
Data
Audio
Transport Protocol Group
RFCOMM
L2CAP
Link Manager
Baseband
RF
Bluetooth Protocol Stack
Applications
IP
SDP
Middleware Protocol Group
RFCOMM
Data
L2CAP
Additional transport protocols to allow Audio Link Manager
existing and new applications to
Baseband
operate over Bluetooth. Packet based
RF
telephony control signaling protocol
also present. Also includes Service
Discovery Protocol.
Bluetooth Protocol Stack
Applications
IP
Application Group
SDP
RFCOMM
Data
Consists of Bluetooth aware as
well as un-aware applications.
Audio
L2CAP
Link Manager
Baseband
RF
Link Manager Protocol
Applications
IP
SDP
RFCOMM
Data
Audio
L2CAP
Link Manager
Baseband
RF
LMP
Setup and management
of Baseband connections
• Piconet Management
• Link Configuration
• Security
L2CAP
Applications
IP
SDP
RFCOMM
L2CAP - Logical Link Control
and Adaptation Protocol
Data
Audio
L2CAP
Link Manager
Baseband
RF
L2CAP provides
• Protocol multiplexing
• Segmentation and
Re-assembly
• Quality of service negotiation
RFCOMM (Radio Frequency Communication)
-- Serial Port Emulation using RFCOMM
Applications
IP
SDP
RFCOMM
Data
Audio
L2CAP
Link Manager
Baseband
RF
Serial Port
Serial Port emulation on
top of a packet oriented
link
• Similar to HDLC (High level
Data Link Control protocol)
• RS232
• For supporting legacy apps
Usage Models
•
•
•
•
•
•
File transfer
Internet bridge
LAN access
Synchronization
Three-in-one phone
Headset
Piconets and Scatternets
• Piconet
– Basic unit of Bluetooth
networking
– Master and one to seven slave
devices
– Master determines channel
and phase
• Scatternet
– Device in one piconet may
exist as master or slave in
another piconet
– Allows many devices to share
same area
– Makes efficient use of
bandwidth
Physical Links between Master and
Slave
• Synchronous connection oriented (SCO)
– Allocates fixed bandwidth between point-to-point
connection of master and slave
– Master maintains link using reserved slots
– Master can support three simultaneous links
• Asynchronous connectionless (ACL)
– Point-to-multipoint link between master and all slaves
– Only single ACL link can exist
Connection Setup
• Inquiry（查询消息）
– Master 查找附近的蓝牙
设备，以便通过收集来自
从节点响应查询消息中得
到该节点的设备地址（
48b）和时钟
• Inquiry – scan（查询扫描）
– Slave设备周期地监听来自其他设备的查询消
息，以便自己能被发现,并在监听到后发送它
的地址和时钟信息。
Connection Setup
• Page （寻呼）
– Master 通过在不同的跳频序列发送消息，来激活一个从
节点, 并建立连接。调频序列由slaver的地址码计算出
• Page – scan（寻呼扫描）
– Slaver 周期性地在扫描窗间隔时间内唤醒自己，并监听
自己的访问码， Slaver节点每隔1.28s在这个扫描窗上根
据寻呼跳频序列选择一个扫描频率
Master
Active Slave
Parked Slave
-Connected
-Not in Pico
Standby
Bluetooth Packet Fields
• Access code – used for timing synchronization,
offset compensation, paging, and inquiry
• Header – used to identify packet type and carry
protocol control information
• Payload – contains user voice or data and payload
header, if present
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
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
72
54
access code packet header
4
preamble
64
sync.
(4)
(trailer)
3
S address
4
type
0-2745
payload
1
flow
bits
1
ARQN
1
SEQN
8
HEC
bits
WPAN: IEEE 802.15
•
•
802.15-2: Coexistence
– Coexistence of Wireless Personal Area Networks (802.15) and
Wireless Local Area Networks (802.11), quantify the mutual
interference
802.15-3: High-Rate
– Standard for high-rate (20Mbit/s or greater) WPANs, while still
low-power/low-cost
– 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
ZigBee
• ZigBee - a specification set of high level communication
protocols designed to use small, low power digital radios
based on the IEEE 802.15.4 standard for wireless
personal area networks (WPANs)
• This technology is designed to be simpler and cheaper
than other WPANs (such as Bluetooth)
• ZigBee uses the IEEE 802.15.4 Low-Rate Wireless
Personal Area Network (WPAN) standard to describe its
lower protocol layers—the physical layer (PHY), and the
medium access control (MAC) portion of the data link
layer (DLL).
ZigBee Applications
monitors
sensors
automation
control
monitors
diagnostics
sensors
INDUSTRIAL &
COMMERCIAL
CONSUMER
ELECTRONICS
TV
VCR
DVD/CD
remote
ZigBee
PERSONAL
HEALTH CARE
consoles
portables
educational
Reference from ZigBee Alliance Inc.
LOW DATA-RATE
RADIO DEVICES
TOYS &
GAMES
HOME
AUTOMATION
PC &
PERIPHERALS
security
HVAC
lighting
closures
mouse
keyboard
joystick
Development of the Standard
APPLICATION
Customer
ZIGBEE STACK
SILICON
ZigBee
Alliance
IEEE
802.15.4
• ZigBee Alliance
– 50+ companies
– Defining upper layers of
protocol stack: from network
to application, including
application profiles
• IEEE 802.15.4 Working Group
– Defining lower layers : MAC
and PHY
IEEE 802.15.4 Overview
• Wireless Personal Area Networks (WPANs)
– short distance
– small (ultra low complexity)
– low duty-cycle (<0.1%)
– power efficient (the most important factor)
– inexpensive (ultra low cost) solutions.
• Typically operating in the Personal Operating Space (POS)
of 10 meters.
• Supporting star and peer-to-peer topologies
– controlled by the PAN coordinator
IEEE 802.15.4 standard
• Includes layers up to and including Link Layer Control
– LLC is standardized in 802.1
• Supports multiple network topologies including Star,
Cluster Tree and Mesh
• Channel scan for beacon is included, but it is left to the
network layer to implement dynamic channel selection
ZigBee Application Framework
• Low complexity:
26 service primitives
versus
131 service primitives
for 802.15.1
(Bluetooth)
Networking App Layer (NWK)
Data Link Controller (DLC)
IEEE 802.15.4 LLC
IEEE 802.2
LLC, Type I
IEEE 802.15.4 MAC
IEEE 802.15.4
868/915 MHz PHY
IEEE 802.15.4
2400 MHz PHY
IEEE 802.15.4 Features
• Media access is contention based.
– Using carrier sense multiple access with collision avoidance
(CSMA/CA) MAC protocol
– Similar to IEEE 802.11 CSMA/CA protocol, but not the same
• Provide the optional Superframe structure
– The PAN coordinator periodically allocates guaranteed time
slots (GTS) to low latency devices
•
Dynamic device addressing
– Two kinds of address of a device
– 16-bit Short Address
– 64-bit Extended Address
•
Fully acknowledged protocol for transfer reliability.
Device Classes
• There are two different device types :
– A full function device (FFD)
– A reduced function device (RFD)
• The FFD can operate in three modes serving
– Device
– Coordinator
– PAN coordinator
• The RFD can only operate in a mode serving:
– Device
• Coordinator provides synchronization information to other
devices
FFD vs RFD
• Full function device (FFD)
– Any topology
– Network coordinator capable
– Talks to any other device
• Reduced function device (RFD)
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–
–
–
Limited to star topology
Cannot become a network coordinator
Talks only to a network coordinator
Very simple implementation
Network Topologies
• Star and Peer2Peer Topologies
Network Topologies
• Star network formation:
– An FFD may establish its own network and become the PAN
coordinator.
– All star networks operate independently.
– Choosing a PAN identifier, which is not currently used by
any other network within the radio sphere of influence.
– Both FFDs and RFDs may join the network.
• Peer-to-peer network formation:
– Each device is capable of communicating with any other
device.
– One FFD device will be nominated as the PAN coordinator.
Star Topology
• Home Application
FFD
RFD
FFD
PAN coordinator
RFD
RFD
RFD
FFD
Cluster Tree Topology
• Only one PAN coordinator
• No detail yet
Cluster Head
PAN coordinator
Cluster Tree Establishment
• 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 (PANID) and broadcasting
beacon frames to neighboring devices.
• A candidate device receiving a beacon frame may request to join
the network at the CLH.
• If the PAN coordinator permits the device, it will add the new
device as a child device in its Access Control List (ACL).
• The newly joined device will add the CLH as its parent in its ACL,
and begin transmitting periodic beacons.
• Other candidate devices may then join the network at that device.
A larger network (PAN) is possible by forming a mesh of multiple
neighboring clusters.
• The PAN coordinator may instruct a device to become the CLH of
a new cluster adjacent to the first one.
• Other devices gradually connect and form a multi-cluster network
structure.
Addressing Methods
• Two or more devices with a POS communicating on the same
physical channel constitute a WPAN which includes at least one
FFD (PAN coordinator)
• Each independent PAN will select a unique PAN identifier
• All devices operating on a network shall have unique 64-bit
extended address. This address can be used for direct
communication in the PAN
• The address can use a 16-bit short address, which is allocated
by the PAN coordinator when the device associates
• Addressing modes:
– Network + device identifier (star)
– Source/destination identifier (peer-peer)
– Source/destination cluster tree + device identifier (cluster tree)
MAC/PHY Functions
• Functions in PHY sublayer
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–
–
–
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activation and deactivation of the radio transceiver
energy detection
link quality indication
clear channel assessment (CCA) - carrier sense
transmitting/receiving bit stream
• Functions in MAC sublayer
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–
–
–
–
–
–
–
beacon management
channel access (slotted or unslotted CSMA/CA)
guarantee time slot management (QoS)
frame validation
acknowledged frame delivery
association
disassociation
security mechanisms (AES)
PHY Specifications
• The standard specifies two PHYs :
– 868 MHz/915 MHz direct sequence spread
spectrum (DSSS) PHY (11 channels)
• 1 channel (20Kb/s) in European 868MHz band
• 10 channels (40Kb/s) in 915 (902-928)MHz ISM band
– 2450 MHz direct sequence spread spectrum
(DSSS) PHY (16 channels)
• 16 channels (250Kb/s) in 2.4GHz band
PHY Specification
• PHY functionalities:
–
–
–
–
–
–
Activation and deactivation of the radio transceiver
Energy detection within the current channel
Link quality indication for received packets
Clear channel assessment for CSMA-CA
Channel frequency selection
Data transmission and reception
PHY Specification
Operating Frequency Range
BAND
2.4 GHz
ISM
868 MHz
915 MHz
ISM
COVERAGE
DATA RATE
CHANNEL(S)
Worldwide
250 kbps
16
Europe
20 kbps
1
Americas
40 kbps
10
• A total of 27 channels, numbered 0 to 26, are available across
the three frequency bands.
• 16 channels are for 2450 MHz, 10 are for 915 MHz an 1 is for
868 MHz.
PHY Parameters
• Transmit Power
– Capable of at least 1 mW
– Power reduction capability required if > 16 dBm
(reduce to < 4 dBm in single step)
• Transmit Center Frequency Tolerance
–  40 ppm
• Receiver Sensitivity
– -85dBm (2450 MHz)
– -92dBm (868/915 MHz)
– 1% Packet Error Rate in PSDU = 20 Bytes)
• RSSI Measurements
–
–
–
Packet strength indication
Clear channel assessment
Dynamic channel selection
PHY PDU Format (PPDU)
•
PHY Packet Fields
– A synchronization header
• Preamble (32 bits) – 32 binary zeros used for synchronization
• Start of Packet Delimiter (8 bits) – 10100111
– A PHY header
• PHY Header (8 bits) – 7-bit frame length (0-127) and 1-bit
reserved
– A payload
• PSDU (0 to 127 bytes) – Data field
4 Bytes
1 Byte
1 Byte
Preamble
Start of
Packet
Delimiter
PHY
Header
6 Bytes
PHY Service
Data Unit (PSDU)
0-127 Bytes
MAC Options
• Two channel access mechanisms
– Non-beacon network
• Standard CSMA-CA communications + ACK
• Non-beacon mode is useful in situations where only light
traffic is expected
– Beacon-enabled network
• Superframe structure
– Set up by network coordinator to transmit beacons at
predetermined intervals
– 15ms to 252sec, slotted CSMA-CA
– In general, the ZigBee protocols minimize the time the
radio is on, so as to reduce power use.
• In beaconing networks, nodes only need to be active
while a beacon is being transmitted.
• In non-beacon-enabled networks, power consumption is
decidedly asymmetrical: some devices are always active,
while others spend most of their time sleeping.
Example of Non-Beacon Net
• Commercial or home security
– Client units (intrusion sensors, motion detectors, glass break
detectors, standing water sensors, loud sound detectors, etc)
• Sleep 99.999% of the time
• Wake up on a regular yet random basis to announce their
continued presence in the network (“12 o’clock and all’s
well”)
• When an event occurs, the sensor wakes up instantly and
transmits the alert (“Somebody’s on the front porch”)
– The ZigBee Coordinator, mains powered,
has its receiver on all the time and
so can wait to hear from each of
these stations
• Since ZigBee Coordinator has “infinite”
source of power it can allow clients
to sleep for unlimited periods of time
to allow them to save power
Example of Beacon Network
• Now make the ZigBee Coordinator battery-operated
also
– Client registration to the network
• Client unit when first powered up listens for the
ZigBee Coordinator’s network beacon (interval
between 0.015 and 252 seconds)
• Register with the coordinator and look for any
messages directed to it
• Return to sleep, awaking on a schedule
specified by the ZigBee Coordinator
– Once client communications are completed,
ZigBee coordinator also returns to sleep
• Application examples: environmental sensors in the
forest
数据到主协调器的通信顺序
Beacon-enabled network
• 从设备监听网络的信标
• 从设备与超帧结构进行同步
• 从设备使用有时隙的CSMA-CA向主协调器发送数
据帧
• 当主协调器接收到该数据帧后，将返回确认帧
数据到主协调器的通信顺序
Non-Beacon-enabled network
Beacon-enabled network
主协调器发送数据
•• 从设备从网络信标中发现存在有主协调器要发送
主协调器收到数据请求命令后，返回一个确认
从设备收到该数据帧后，将返回一个确认
主协调器收到确认帧后，将数据信息从主
主协调器发送网络信标中表明存在有要传
给它的数据信息时，采用有时隙的CSMA-CA机制
帧，并采用有时隙的CSMA-CA机制，发送要
帧，表示该数据传输事务已处理完成
协调器的信标未处理信息列表中删除
输的数据信息。
，发送一个数据请求命令
。
传输的数据信息帧
Non-Beacon-enabled network
主协调器发送数据
• 非信标网络中传输数据给从设备时，主协调器存
储着要传输的数据，由从设备先发送请求数据传
输命令后，才能进行数据传输
MAC Specifications
• Superframe Structure
– Optional (named as beacon-enabled network)
– The format of the superframe is define by the PAN coordinator
– Bounded by network beacons and sent by the PAN coordinator
– Divided into 16 equally sized slots and beacon is transmitted in
the first slot
– It consists of two periods
• Contention Access Period (CAP)
• Contention Free Period (CFP)
– Objectives of the beacons
• synchronize
• identify the PAN
• describe the structure of the superframes
MAC Specifications
•
•
•
•
•
•
The superframe can have an active and an inactive portion.
• During the inactive portion the coordinator shall not
interact with its PAN and may enter a low power mode.
The PAN coordinator may allocate portions of the active
superframe to some applications and these portions are
called guaranteed time slots (GTSs).
The GTSs comprise the contention free period (CFP).
The PAN coordinator may allocate up to 7 GTSs at the same
time
A GTS may occupy more than one slot period
A sufficient portion of the CAP shall remain for contention.
MAC Specifications
• Any device wishing to communicate during the CAP
between two beacons shall compete with other devices
using a slotted CSMA-CA mechanism.
• All transactions shall be completed by the time of the next
network beacon
• If the coordinator does not wish to use a superframe
structure, it can turn off the beacon transmissions
– named as non beacon-enabled network
– Using Unslotted CSMA/CA
Superframe Structure
•
The structure of this superframe is described by the values of
macBeaconOrder (BO) and macSuperframeOrder (SO).
– The macBeaconOrder describes the interval at which the coordinator
shall transmit its beacon frames.
– The macSuperframeOrder describes the length of the active portion of
the superframe, which includes the beacon frame.
Superframe Structure
• The values of BO and the beacon interval (BI) are related as
follows:
BI = aBaseSuperframeDuration  2BO symbols, if 0BO14
• The values of SO and the superframe duration (SD) are related as
follows:
SD = aBaseSuperframeDuration  2SO symbols, if 0SOBO14
• Note : If BO = 15, the coordinator will not transmit beacon and the
value of SO shall be ignored. (non beacon-enable network)
Moreover, macRxOnWhenIdle defines whether the receiver is
enabled during periods of transceiver inactivity (default : FALSE)
• If SO = 15, the superframe will not be active after the beacon.
• PANs that wish to use the superframe structure shall set
0SOBO14.
General Frame Format
PHY Layer
MAC
Layer
Payload
Synch. Header
(SHR)
PHY Header
(PHR)
MAC Header
(MHR)
MAC Service Data Unit
(MSDU)
MAC Protocol Data Unit (MPDU)
PHY Service Data Unit (PSDU)
MAC Footer
(MFR)
General MAC Frame Structure
• Four Types of Frames Structure:
– Beacon Frame - used by coordinator
– Data Frame - used for all transfers of data
– Acknowledgment Frame - used for confirming successful frame
reception
– MAC Command Frame - used for handling all MAC peer entity
control transfers
Beacon Frame Format
Data Frame Format
Acknowledgement Frame
Format
MAC Command Frame Format
CSMA/CA Mechanism
• unslotted CSMA/CA:
– A device waits for a random period without carrier
sense.
– If the channel is idle, following the random backoff,
it transmits its data. Otherwise, it waits for another
random period before retry.
• slotted CSMA/CA:
– It is similar to the unslotted CSMA/CA but follows
the backoff slot boundary.The backoff slots are
aligned with the start of the beacon transmission.
CSMA/CA Mechanism
• Frame Acknowledgment
– If the originator does not receive an ACK after
some period. It will retry the frame transmission. If
an ACK is still not received after several retries,
the originator can choose either to terminate or to
try again.
• Power Consumption Considerations
– Battery powerd devices will require duty-cycling to
reduce power consumption. These devices will
spend most of their operational life in a sleep
state. They shall periodically listen to the RF
channel to determine whether a message is
pending.
CSMA-CA Algorithm
•
The LR-WPAN uses two types of channel access mechanism,
depending on the network configuration.
1. Non beacon-enabled networks use an unslotted CSMA-CA
channel access mechanism.
2. Beacon-enabled networks use a slotted CSMA-CA channel
access mechanism.

In both cases, the algorithm is implemented using units of time
called backoff periods, where one backoff period shall be equal
to aUnitBackoffPeriod (=20) symbols.
CSMA-CA Algorithm
• In slotted CSMA-CA, the backoff period boundaries shall be
aligned with the superframe slot boundaries
– the start of the first backoff period of each device is aligned with the
start of the beacon transmission.
• In unslotted CSMA-CA, the backoff periods of one device are
not related in time to the backoff periods of any other device in
the PAN.
• The CSMA-CA algorithm shall not be used for the transmission
of
– beacon frames
– acknowledgement frames
– data frames transmitted in the CFP.
CSMA-CA Algorithm
• Each device shall maintain three variables for each transmission
attempt:
– NB (no. of backoff – also known as retry count) (4)
– CW (contention window size, perform PHY CCA)
– BE (backoff exponent)
• NB is the number of times the CSMA-CA algorithm was required
to backoff while attempting the current transmission; this value
shall be initialized to 0 before each new transmission attempt.
• CW is the contention window length, defining the number of
backoff periods that need to be clear of channel activity before
the transmission can commence; this value shall be initialized to
2 before each transmission attempt. The CW variable is only
used for slotted CSMA-CA.
• BE is the backoff exponent which is related to how many backoff
periods a device shall wait before attempting to assess a
channel.
Flow Chart
Frame Transmission
• If the source address (SA) field is not present, the originator of
the frame shall be assumed to be the PAN coordinator.
• If the destination address (DA) field is not present, the recipient
of the frame shall be assumed to be the PAN coordinator.
• If both SA and DA addresses are present, the MAC shall
compare the destination and source PAN identifiers
– If the PAN identifiers are identical, the intra PAN subfield of the
frame control field shall be set to 1 and the source PAN identifier
shall be omitted from the transmitted frame.
• Save bandwidth, only carry the destination PAN identifier
– If the PAN identifiers are different, the intra PAN subfield of the
frame control field shall be set to 0 and both destination and source
PAN identifier fields shall be included in the transmitted frame.
Frame reception and rejection
1. The frame type subfield shall not contain an illegal frame type.
2. If the frame type indicates that the frame is a beacon frame,
the source PAN identifier shall match macPANId unless
macPANId is equal to 0xffff, in which case the beacon frame
shall be accepted regardless of the source PAN identifier.
3. If a destination PAN identifier is included in the frame, it shall
match macPANId or shall be the broadcast PAN identifier
(0xffff).
4. If a short DA is included in the frame, it shall match either
macShortAddress or the broadcast address (0xffff). Otherwise,
it shall match aExtendedAddress.
5. If only SA fields are included in a data or MAC command frame,
the frame shall only be accepted if the device is a PAN
coordinator and the source PAN identifier matches macPANId.
GTS allocation and management
• Guaranteed time slot (GTS) allows a device to
operate on the channel without interferences.
• A GTS only be allocated by the PAN coordinator and
is used for communications between PAN
coordinator and device.
• A data frame transmitted in an allocated GTS shall
use only short address
• The PAN coordinator shall send all frames within a
receive GTS with AR=1
• The PAN coordinator may allocate up to seven GTSs
at the same time, provided there is sufficient capacity
in the superframe.
GTS allocation and management
• A single GTS occupies one or more superframe slots
• GTSs are allocated on a first-come-first-served basis and all
GTSs shall be placed contiguously at the end of the superframe
and after the CAP
• For each GTS, the PAN coordinator records
–
–
–
–
starting slot
length (in superframe slots)
direction
associated device address
• For each allocated GTS, the device records
– starting slot
– length
– direction
ZigBee and Bluetooth
Optimized for different applications
• ZigBee
• Bluetooth
– Smaller packets over
large network
– Mostly Static networks
with many, infrequently
used devices
– Home automation, toys
remote controls
– Energy saver!!!
– Larger packets over small
network
– Ad-hoc networks
– File transfer; streaming
– Cable replacement for items
like screen graphics,
pictures, hands-free audio,
Mobile phones, headsets,
PDAs, etc.
ZigBee and Bluetooth
• Bluetooth and 802.15.4 transceiver physical
characteristics are very similar
• Protocols are substantially different and designed
for different purposes
• 802.15.4 designed for low to very low duty cycle
static and dynamic environments with many active
nodes
• Bluetooth designed for high QoS, variety of duty
cycles, moderate data rates in fairly static simple
networks with limited active nodes
Summary
• 802.15.1
• 802.15.4 (ZigBee)