technology and example standards
TRANSCRIPT
Technology and Example Standards
The right technology/standard for the problem/environment??
1
Characteristics of selected wireless link standards
Indoor 10-30m
Outdoor 50-200m
Mid-range
outdoor 200m – 4 Km
Long-range
outdoor 5Km – 20 Km
.056
.384
1
4
5-11
54
IS-95, CDMA, GSM 2G
UMTS/WCDMA, CDMA2000 3G
802.15
802.11b
802.11a,g
UMTS/WCDMA-HSPDA, CDMA2000-1xEVDO 3G cellular
enhanced
802.16 (WiMAX)
802.11a,g point-to-point
200 802.11n
Data
rate
(M
bps) data
2
Differences in bandwidths primarily from ...
Physical layer Spectrum allocation (wave length)
Frequency; channel width; time multiplexing
Signal-to-Noise; BER; Error correction; etc.
MAC layer (sub-layer in data link layer) Multiple access techniques
E.g., FDMA, TDMA, CDMA, SDMA, OFDMA
3
Frequency band spectrum
spectrum allocated by global and national agencies
(Less sensitive to obstacles) Low frequency
(More sensitive to obstacles) High frequency
ELF (30-300Hz)
Visible light (400-900THz)
Telephone; AM broadcast Cell phone; Satellite Microwave links
4
IEEE 802.11 Wireless LAN
802.11b 2.4-5 GHz unlicensed spectrum
up to 11 Mbps
direct sequence spread spectrum (DSSS) in physical layer
• all hosts use same chipping code
802.11a 5-6 GHz range
up to 54 Mbps
802.11g 2.4-5 GHz range
up to 54 Mbps
802.11n: multiple antenna
2.4-5 GHz range
up to 200 Mbps
all use CSMA/CA for multiple access
all have base-station and ad-hoc network versions
5
6
802.11 LAN architecture
Wireless host communicates with base station
base station = access point (AP)
Basic Service Set (BSS) (aka “cell”) in infrastructure mode contains:
wireless hosts
access point (AP)
ad hoc mode: hosts only
BSS 1
BSS 2
Internet
hub, switch or router
AP
AP
7
802.11: Cells, channels, association
802.11b has 11 channels
Channels 1, 6, and 11 are non-overlapping
8
802.11: Cells, channels, association
802.11b has 11 channels
Channels 1, 6, and 11 are non-overlapping
Each AP coverage area is called a “cell”
Wireless nodes can roam between cells
AP
AP
AP AP
AP AP
Channel 1
Channel 6
Channel 1 Channel 11
Channel 6
Channel 1
9
802.11: Cells, channels, association
802.11b has 11 channels
Channels 1, 6, and 11 are non-overlapping
Each AP coverage area is called a “cell”
Wireless nodes can roam between cells
AP
AP
AP AP
AP AP
Channel 1
Channel 6
Channel 1 Channel 11
Channel 6
Channel 1
AP admin chooses frequency for AP
interference possible: channel can be same as that chosen by neighboring AP!
10
802.11: Channels, association
host: must associate with an AP scans channels, listening for beacon frames
containing AP’s name (SSID) and MAC address selects AP to associate with may perform authentication typically run DHCP to get IP address in AP’s subnet
11
802.11: passive/active scanning
AP 2 AP 1
H1
BBS 2 BBS 1
1 2 2
3 4
Active Scanning:
(1) Probe Request frame broadcast from H1
(2) Probes response frame sent from APs
(3) Association Request frame sent: H1 to selected AP
(4) Association Response frame sent: selected AP to H1
AP 2 AP 1
H1
BBS 2 BBS 1
1
2 3
1
Passive Scanning: (1) Beacon frames sent from APs (2) Association Request frame sent:
H1 to selected AP (3) Association Response frame sent:
selected AP to H1
12
frame
control duration
address
1
address
2
address
4
address
3 payload CRC
2 2 6 6 6 2 6 0 - 2312 4
seq
control
802.11 frame: addressing
Address 2: MAC address of wireless host or AP transmitting this frame
Address 1: MAC address of wireless host or AP to receive this frame
Address 3: MAC address of router interface to which AP is attached
Address 4: used only in ad hoc mode
13
802.11: advanced capabilities
Rate Adaptation
base station, mobile dynamically change transmission rate (physical layer modulation technique) as mobile moves, SNR varies
QAM256 (8 Mbps)
QAM16 (4 Mbps)
BPSK (1 Mbps)
10 20 30 40
SNR(dB)
BE
R
10-1
10-2
10-3
10-5
10-6
10-7
10-4
operating point
1. SNR decreases, BER increase as node moves away from base station
2. When BER becomes too high, switch to lower transmission rate but with lower BER
14
802.11: advanced capabilities
Power Management node-to-AP: “I am going to sleep until next beacon frame”
AP knows not to transmit frames to this node
node wakes up before next beacon frame
beacon frame: contains list of mobiles with AP-to-mobile frames waiting to be sent
Every 100ms (250s wakeup time)
node will stay awake if AP-to-mobile frames to be sent; otherwise sleep again until next beacon frame
Explicit pull request
Note: Nodes with nothing to send/receive can save 99% of energy
15
16
A typical Bluetooth data frame
17
Bluetooth Networking • Piconets and Scatternets: – Bluetooth devices are organized in local networks called piconets – up to eight devices can be part of a piconet – devices are divided in master and slaves – the master controls the utilization of the radio channel (e.g. frequency-hopping sequence and timing) in the communication with the slaves – a slave may communicate only with the master and when allowed by the master – a device may belong to different piconets and may be both a master and a slave in two different piconets – a network formed by several connected piconets is called a scatternet
18
M radius of
coverage
S
S S
P
P
P
P
M
S
Master device
Slave device
Parked device (inactive) P
802.15: personal area network (PAN)
less than 10 m diameter
replacement for cables (mouse, keyboard, headphones)
ad hoc: no infrastructure
master/slaves: slaves request permission to
send (to master)
master grants requests
802.15: evolved from Bluetooth specification 2.4-2.5 GHz radio band
up to 721 kbps
19
20
Two Popular 2.4 GHz Standards:
IEEE 802.11 (WiFi) Fast (11 Mbps)
High power
Long range
Single-purpose
Typically channel 1, 6, or 11
Ethernet replacement
Easily available
Bluetooth Slow (1 Mbps)
Low power
Short range
Flexible
Frequency hopping
Cable replacement (e.g., device-to-device)
21
Example
What technology/device?
22
Example
Many devices and technologies sharing the medium … resulting in different degrees of interference
23
Figures from: A. Mahanti et al., ”Ambient Interference Effects in Wi-Fi Networks”, Proc. IFIP Networking, 2010.
Example: Channel Utilization
Channel utilization: The % of time a transmission is present from a known RF source, in a given channel
Channels 1 and 6, utilization peaked near 60%, while for channel 11 it was over 90%.
Channel 11 spikes caused due to microwave ovens, cordless phones, and other fixed-frequency devices.
24
Figure from: A. Mahanti et al., ”Ambient Interference Effects in Wi-Fi Networks”, Proc. IFIP Networking, 2010.
25
802.16: WiMAX (MAN)
like 802.11 & cellular: base station model transmissions to/from
base station by hosts with omnidirectional antenna
base station-to-base station backhaul with point-to-point antenna
unlike 802.11: range ~ 6 miles (“city
rather than coffee shop”) ~14 Mbps
point-to-multipoint
point-to-point
26
802.16: WiMAX: downlink, uplink scheduling
transmission frame
down-link subframe: base station to node
uplink subframe: node to base station
pre
am
.
DL-
MAP UL-
MAP
DL
burst 1 SS #1
DL
burst 2
DL
burst n
Initial
maint.
request
conn.
downlink subframe
SS #2 SS #k
uplink subframe
…
…
…
…
base station tells nodes who will get to receive (DL map) and who will get to send (UL map), and when
WiMAX standard provide mechanism for scheduling, but not scheduling algorithm
27
28
Mobile
Switching
Center
Public telephone network, and Internet
Mobile
Switching
Center
Components of cellular network architecture
connects cells to wide area net manages call setup (more later!) handles mobility (more later!)
MSC
covers geographical region base station (BS) analogous to 802.11 AP mobile users attach to network through BS air-interface: physical and link layer protocol between mobile and BS
cell
wired network
29
• Frequency reuse: use the same
frequency spectrum in different
set of cells
• Cells that reuse the same
frequency must be distant enough
for avoiding interference
• Transmission power control
• Migration of a mobile station from
one cell to another with
continuance of communication ->
handoff
Components of cellular networks, cont’d
30
31
More slides …
32
Cellular standards: brief survey
2G systems: voice channels IS-136 TDMA: combined FDMA/TDMA (north
america)
GSM (global system for mobile communications): combined FDMA/TDMA most widely deployed
IS-95 CDMA: code division multiple access
GSM Don’t drown in a bowl
of alphabet soup: use this
for reference only
33
Cellular standards: brief survey
2.5 G systems: voice and data channels for those who can’t wait for 3G service: 2G extensions
general packet radio service (GPRS) evolved from GSM
data sent on multiple channels (if available)
enhanced data rates for global evolution (EDGE) also evolved from GSM, using enhanced modulation
data rates up to 384K
CDMA-2000 (phase 1) data rates up to 144K
evolved from IS-95
34
Cellular standards: brief survey
3G systems: voice/data Universal Mobile Telecommunications Service (UMTS)
data service: High Speed Uplink/Downlink packet Access (HSDPA/HSUPA): 3 Mbps
CDMA-2000: CDMA in TDMA slots data service: 1xEvlution Data Optimized (1xEVDO)
up to 14 Mbps 4G systems: voice/data ….. more (and more interesting) cellular topics due to mobility (stay
tuned for details)
35
36
More slides …
37
38
• Station: a device containing 802.11 equipment
• Basic Service Set (BSS): set of stations controlled by a coordination function
• Coordination function: logical function determining when a station can receive and send data in a BSS
• Distribution System (DS): a system connecting a set of BSS and integrated LANs to create an extended service set (ESS)
• Extended Service Set: a set of BSS and LANs appearing as a single unit to the LLC layer of the component stations
• Access point (AP) : entity providing access to the distribution system
IEEE 802.11 Architecture
39
• IEEE 802.11 define 9 services: – 6 services for supporting delivery of MAC service data units (MSDU)
between stations – 3 services for LAN access and confidentiality
• Service provider type: – station: services implemented in stations and access point stations
(APs) – distribution system (DS): services between BSSs implemented in
access point stations or dedicated devices
IEEE 802.11 Services
40
41
Bluetooth - Channel control in a piconet [1]
• Two major states of a Bluetooth device: – Standby: low-power state
– Connection: the device is connected
• Seven states for adding new slaves to a piconet: – Page – device issued a page (used by master)
– Page scan – device is listening for a page
– Master response – master receives a page response from slave
– Slave response – slave responds to a page from master
– Inquiry – device has issued an inquiry for identity of devices
within range
– Inquiry scan – device is listening for an inquiry
– Inquiry response – device receives an inquiry response
42
Bluetooth - Channel control in a piconet [2]
43
Bluetooth - Inquiry and Page Procedure [1]
Inquiry Procedure: Potential master identifies devices in range that wish to
participate – transmits an identification ID packet with inquiry
access code (IAC) – occurs in Inquiry state Devices receives inquiry – enter Inquiry Response state – return data with address and timing information (in an
FHS packet) – slave moves to Page Scan state or returns to Inquiry
Scan
44
Bluetooth - Inquiry and Page Procedure [2]
Page Procedure • Master uses device address to calculate a page
frequency-hopping sequence • Master pages with ID packet and device access code
(DAC) of specific slave • Slave responds with ID DAC packet • Master responds with a special FHS packet containing
its address and real-time Bluetooth clock value • Slave confirms master’s FHS packet reception with a
ID DAC packet • Slaves moves to Connection state
Connection state control for slaves • Master send a Poll packet to verify that a slave has
switched on master timing and channel frequency • Slave responds with any packet
45
Bluetooth - Slave Connection State Modes
Active – slave participates in piconet – listens, transmits and receives packets – master sent regularly synchronization data
Sniff – slave listens only on specified slots – master indicate a reduced number of slots – slave can operate in reduced power mode when not listening
Hold – slave may participate partially in the piconet – slave in reduced power status – slave does not support ACL packets – slave may participate in SCO exchanges
Park – slave does not participate currently in the piconet – slave still retained as part of the piconet – device receive a parking address and loses its active member
address – piconet may then have more than 7 slaves, but only 7 are active
46
47
48
Other PAN’s: The ANT protocol stack Wireless sensor communications protocol stack
2.4 GHz RF spectrum (i.e., the ISM band)
Establishes rules for co-existence, data representation, signaling, authentication, and error detection
Low computational overhead and high efficiency Low power consumption by the radios
Targeted at the sports sector, particularly fitness and cycling performance monitoring. Transceivers are embedded in equipment such as heart
rate belts, watches, cycle power and cadence meters, and distance and speed monitors
49