Wireless Technologies

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Wireless Technologies
802.15
802.11
GPRS
LMDS
WiMAX
3G
802.16
UMTS
WiFi
MMDS
CDMA
FSO
802.20
Bluetooth
VSAT
EVDO
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Wireless LANs

• Well start first with wireless LANs, then move
  on to Bluetooth, followed by wireless WANs

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A BSS without an AP is called an ad hoc
network a BSS with an AP is called an
infrastructure network.
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Figure 14.1 Basic service sets (BSSs)
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Figure 14.2 Extended service sets (ESSs)
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WLAN Standards
802.11 Release Freq Typ Throughput Max Net
Bitrate Mod ---- 1997 2.4 GHz 0.9 Mbps
2 IR/FHSS/DSSS a 2003 5 23
54 OFDM b 1999 2.4 4.3 11 DSSS
g 2003 2.4 19 54 OFDM n 2009 2.4
/ 5 74 600 OFDM More on each of these
a little later.
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WLAN Performance (line rate)
Data Source Cisco Networking Professional
On-Line Live Tech Talk
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Creating WLAN Connections

• An Access Point (AP) broadcasts is SSID (service
  set identifier) roughly every 100 ms and at 1
  Mbps (to accommodate the slowest client)
• The Wi-Fi standard leaves connection criteria
  open to the client
• The Wi-Fi spectrum is divided into a fixed number
  of channels
• 11 in North America
• 13 in most of Europe and China
• 14 in Japan

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Creating WLAN Connections

• But not all channels are used due to the concern
  of overlapping frequencies
• In North America, only channels 1, 6 and 11 are
  recommended for 802.11b and g.
• IEEE 802.11a has 42 channels, of which only 24
  are used in North America, from which only about
  12 are used to reduce overlapping frequencies

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Figure 14.3 MAC layers in IEEE 802.11 standard
FHSS - frequency hopping spread spectrum DSSS -
direct sequence spread spectrum OFDM - orthogonal
frequency division multiplexing
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Figure 14.4 CSMA/CA flowchart
DIFS distributed interframe space SIFS
short interframe space
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Figure 14.5 CSMA/CA and NAV (Network Allocation
Vector)
When a station sends its RTS, it includes a time
of how long it needs the medium. Other stations
then set their NAV timer to this time so they
dont transmit. DIFS Distributed interframe
space SIFS short interframe space
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Figure 14.6 Example of repetition interval
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Figure 14.7 Frame format
FC Frame Control D duration of the transmission
that is used to set the value of NAV SC sequence
control defines the sequence number of the frame
to be used in flow control
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Table 14.1 Subfields in FC field
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Figure 14.8 Control frames
FC Frame Control D duration of the transmission
that is used to set the value of NAV
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Frame Types
Three types of frames 1. Management - used for
initial communication between stations and
access points 2. Control - used for accessing
the channel (RTS) and acknowledging frames (CTS
or ACK) (See Figure 15-10). 3. Data - used for
carrying data and control information
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Table 14.2 Values of subfields in control frames
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Table 14.3 Addresses
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Case 00 (ad hoc)
11-22-33-01-01-01
11-22-33-02-02-02
A1 11-22-33-01-01-01
DA
A2 11-22-33-02-02-02
SA
A3 BSS ID
A4 not used
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Case 01 (wired to wireless)
wireless 802.11
wired 802.3
11-22-33-01-01-01
11-22-33-02-02-02
99-88-77-09-09-09
A1 (RA) 11-22-33-01-01-01
DA 11-22-33-01-01-01
A2 (TA) 99-88-77-09-09-09
SA 11-22-33-02-02-02
A3 (SA) 11-22-33-02-02-02
A4 not used
RA Wireless Receiver Address TA Wireless
Transmitter Address
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Case 10 (wireless to wired)
wired 802.3
wireless 802.11
11-22-33-01-01-01
11-22-33-02-02-02
99-88-77-09-09-09
A1 (RA) 99-88-77-09-09-09
DA 11-22-33-02-02-02
A2 (TA) 11-22-33-01-01-01
SA 11-22-33-01-01-01
A3 (DA) 11-22-33-02-02-02
A4 not used
RA Wireless Receiver Address TA Wireless
Transmitter Address
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Case 11 (via wireless)
wired 802.3
wireless 802.11
wired 802.3
99-88-77-08-08-08
99-88-77-09-09-09
11-22-33-01-01-01
11-22-33-02-02-02
DA 11-22-33-02-02-02
DA 11-22-33-02-02-02
A1 (RA) 99-88-77-08-08-08
SA 11-22-33-01-01-01
SA 11-22-33-01-01-01
A2 (TA) 99-88-77-09-09-09
A3 (DA) 11-22-33-02-02-02
A4 (SA) 11-22-33-01-01-01
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Figure 14.10 Hidden station problem
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The CTS frame in CSMA/CA handshake can prevent
collision from a hidden station.
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Wireless Bridge
Building B
Building A
Ethernet Backbone
Ethernet Backbone
Case 11
Wireless Bridge
Wireless Bridge
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Wireless Repeater
LAN Backbone
Case 10
Case 11
Case 01
Wireless repeater
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Figure 14.11 Use of handshaking to prevent
hidden station problem
Station C doesnt hear RTS from B, but it does
hear CTS from A, so it knows something is up.
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Figure 14.12 Exposed station problem
C wants to send to D, but hears A talking to B,
so assumes the medium is (incorrectly) busy.
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Figure 14.13 Use of handshaking in exposed
station problem
Looking for a CTS handshake does not work in this
case.
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Table 14.4 Physical layers
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Figure 14.14 Industrial, scientific, and medical
(ISM) band
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IEEE 802.11b

• First modification to the 802.11 standard
• HR-DSSS (High Rate DSSS)
• Baker code (chipping code) and Complementary Code
  Keying (CCK)
• 2.4 GHz (ISM band)
• 2.412 2.484
• Channel
• up to 14 (5MHz per channel)
• Non-overlapping channel 3
• Speed 1 (Baker), 2 (Baker), 5.5 (CCK), and 11M
  bps (CCK)
• Distance 300 ft
• In practice 100 ft
• Interference cordless phone, microwave oven

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IEEE 802.11a

• Higher speed protocol
• 5 GHz (UNII band)
• 5.15 5.825 GHz
• Spread Spectrum Transmission orthogonal
  frequency division multiplexing (OFDM)
• Data rate 6, 9, 12, 18, 24, 36, 48, or 54Mbps
  Mbps
• Distance 60 ft
• Less interference than 802.11b
• More users per AP than 802.11b
• More non-overlapping channels (8/12 vs. 3)

UNII unlicensed national information
infrastructure
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IEEE 802.11g

• Two competing standards to improve 802.11b
• CCK gt PBCC, 22M bps (This is known as 802.11b)
• DSSS gt OFDM, 54M
• Frequency 2.412 2.484G Hz (same as 802.11b)
• Speed up to 54M bps
• Distance comparable to 802.11b
• Shorter distance at higher rate
• Backward compatible with 802.11b
• Caveat so is the performance.
• Spread Spectrum Transmission OFDM (same as
  802.11a)

PBCC Packet Binary Convolution Code
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WLAN Performance
802.11b 802.11a 802.11g
Link Rate (max) 11M bps 54M bps 54M bps
UDP 7.1M bps 30.5M bps 30.5M bps
TCP 5.9M bps 24.4M bps 24.4M bps
The test was conducted in a lab environment, and
the distance is expected to be less than 10m.
Ref. WLAN Testing with IXIA IxChariot, IXIA
White Paper
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802.11n

• It is a standard finally, but many pre-n
  products
• Over-the-air (OTA) data rate 500 Mbps
• MAC performance 200 Mbps
• Improved Channel bandwidth 20MHz gt 40MHz
• Physical layer Multiple-Input-Multiple-Output
  (MIMO)
• An improvement over OFDM
• Backward compatibility 802.11g/a (2.4GHz, and
  5.0GHz)
• Distance/coverage somewhat shorter than 802.11g/a

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MIMO
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14-2 BLUETOOTH
Bluetooth is a wireless LAN technology designed
to connect devices of different functions such as
telephones, notebooks, computers, cameras,
printers, coffee makers, and so on. A Bluetooth
LAN is an ad hoc network, which means that the
network is formed spontaneously.
Topics discussed in this section
ArchitectureBluetooth LayersBaseband Layer L2CAP
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Figure 15.17 Bluetooth details
Radio layer - roughly equivalent to physical
layer. Uses 2.4 GHz ISM divided into 79 channels
of 1 MHz each. Uses FHSS 1600 hops/sec, so each
frequency lasts for only 625 microseconds
(1/1600). This is the dwell time. Basic rate
(BR) uses Gaussian FSK at 1 Mbps, extended
data rate (EDR) uses pi/4-DQPSK for 2 Mbps and
8DPSK for 3 Mbps Baseband layer - roughly
equivalent to MAC sublayer and uses TDD-TDMA
(time-division duplexing TDMA). Similar to
walkie-talkies using different carrier
frequencies.
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Figure 15.17 Bluetooth details
Primary-secondary architecture with up to 7
slaves in a piconet. All devices share the
primarys clock. Packet exchange based on two
ticks of a 312.5 microsec clock.
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Figure 14.19 Piconet
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Figure 14.20 Scatternet
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Figure 14.21 Bluetooth stack Windows CE 5.0
Required L2CAP, SDP, LMP L2CAP Logical Link
Control and Adaptation Protocol used to
multiplex multiple logical connections between
two devices SDP Service Discovery Protocol
allows a device to discover services offered by
other devices LMP Link Management Protocol
used to manage the radio link between 2 devices
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Figure 14.22 Single-secondary communication
Note primary transmits in even slots, secondary
in odd
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Figure 14.23 Multiple-secondary communication
Primary switches between secondaries in
round-robin fashion
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Figure 14.24 Frame format types
Access code 72-bit field normally contains sync
bits and ID of the primary to distinguish the
frame of one piconet from another Address up to
7 secondaries 0 means broadcast Type defines
the type of data coming from the upper layer F
flow control (1 indicates buffer full) A ACK
(bluetooth uses stop and wait) S sequence number
for stop and wait
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Figure 14.25 L2CAP data packet format
L2CAP layer roughly equivalent to LLC layer in
LANs Length length of data coming from upper
layers Channel ID defines a unique ID for the
virtual channel created at this level
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Figure 16.1 Cellular system
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Figure 16.2 Frequency reuse patterns
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1G 2G 2.5G 2.75G 3G 3.5G
4G
HSPA High speed packet access 400-700kbps (or 3G
?)
GPRS 30-50 kbps
UMTS Wideband-CDMA Wireless-CDMA 384kbps
ATT, T-Mobile
LTE? Long-term Evolution 3-5 Mbps
GSM
D-AMPS IS-136
EDGE 75-135kbps iPhone (1st generation)
AMPS
CDMA2000 EV-DV Dead? 3.1 Mbps down 1.8 Mbps up
UMB ?? Ultra- Mobile Broadband WiMax?? Wi-Fi??
?
CDMA2000 EV-DO 1xEV EV IS-856 2.5 Mbps down 154
kbps up Verizon, Sprint
1xRTT CDMA2000 1x IS-2000 144 kbps
CDMA IS-95
iDEN Nextel
EV-DO Rev.A Up to 3.1Mbps
ATT, Verizon, and Alltel now support LTE. What
about WiMax for 4G?
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AMPS is an analog cellular phone system using
FDMA.
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Figure 16.3 Cellular bands for AMPS
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Figure 16.4 AMPS reverse communication band
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Figure 16.5 Second-generation cellular phone
systems
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Figure 16.6 D-AMPS
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D-AMPS, or IS-136, is a digital cellular phone
system using TDMA and FDMA.
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Figure 16.7 GSM bands
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Figure 16.8 GSM
GSM uses TDMA and FDMA concepts GMSK (Gaussian
minimum shift keying) a form of FSK used in
European systems
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Figure 16.9 GSM Multiframe components
Lots of overhead!!
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Figure 16.10 IS-95 CDMA forward (base to mobile)
transmission
19.2 ksps 19.2 kilosignals per second
19.2 ksps signal converted to 64-chip sequence,
giving 1.228 Mcps (mega-chips)
ESN electronic serial number of handset
ESN is used to generate 242 pseudorandom chips,
each having 42 bits. Decimator chooses 1 bit out
of the 64, and then is scrambled with digitized
voice to create privacy.
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Figure 16.11 IS-95 CDMA reverse (mobile to base)
transmission
Each 6 symbols are used to index into a 64x64
Walsh matrix thus each 6-symbol chunk is
replaced (not multiplied as it would be with
CDMA) with a 64-chip code.
A 42-bit unique code is generated by the
mobile hand set and combined with the 307.2 kcps
signal creating a 1.228 Mcps signal.
Note CDMA not used here because no way of
syncing all mobile devices together! Frequency
reuse is 1, since neighboring channels cannot
interfere with CDMA or DSSS transmission.
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In CDMA, one channel carries all transmissions
simultaneously.
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Figure 12.23 Simple idea of communication with
code
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Figure 12.24 Chip sequences
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Figure 12.25 Data representation in CDMA
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Figure 12.26 Sharing channel in CDMA
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Figure 12.27 Digital signal created by four
stations in CDMA
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Figure 12.28 Decoding of the composite signal
for one in CDMA
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Figure 12.29 General rule and examples of
creating Walsh tables
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The number of sequences in a Walsh table needs to
be N 2m.
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Example 12.6
Find the chips for a network with a. Two stations
b. Four stations
Solution We can use the rows of W2 and W4 in
Figure 12.29 a. For a two-station network, we
have 1 1 and 1
-1. b. For a four-station network we have
1 1 1 1, 1 -1 1 -1,
1 1 -1 -1, and 1 -1 -1
1.
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Example 12.7
What is the number of sequences if we have 90
stations in our network?
Solution The number of sequences needs to be 2m.
We need to choose m 7 and N 27 or 128. We can
then use 90 of the sequences as the chips.
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Example 12.8
Prove that a receiving station can get the data
sent by a specific sender if it multiplies the
entire data on the channel by the senders chip
code and then divides it by the number of
stations.
Solution Let us prove this for the first station,
using our previous four-station example. We can
say that the data on the channel D (d1
c1 d2 c2 d3 c3 d4 c4). The receiver
which wants to get the data sent by station 1
multiplies these data by c1.
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Example 12.8 (continued)
When we divide the result by N, we get d1 .
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2.5 Generation iDEN
iDEN (Integrated Dispatch Enhanced Network)

• Functionally the same as MIRS (Motorola
  Integrated Radio System)
• A high-capacity digital trunked radio system
  providing integrated voice and data services to
  its users
• Used by Nextel Communications

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2.5 Generation GPRS
GPRS (General Packet Radio Service)

• The 2.5G version of GSM
• Theoretically allows each user access to 8 GSM
  data channels at once, boosting data transfer
  speeds to more than 100 Kbps (30 Kbps in the real
  world since it only uses 2 GSM channels)
• ATT Wireless, Cingular, T-Mobile

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2.5 Generation 1xRTT
1xRTT (CDMA2000) 1x Radio Transmission
Technology

• The 2.5G backwards compatible replacement for
  CDMA
• 1xRTT will replace CDMA and iDEN
• 1x means that it requires only the same amount
  of spectrum as 2G networks based on CDMA (IS-95)
• Sprint and Verizon

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3rd Generation UMTS
UMTS (Universal Mobile Telecommunications System)

• Also called Wideband CDMA
• The 3G version of GPRS
• UMTS is not backward compatible with GSM, so
  first UMTS phones will have to be dual-mode
• Based on TDMA, same as D-AMPS and GSM

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3rd Generation 1xEV
1xEV (1x Enhanced Version)

• The 3G replacement for 1xRTT
• Will come in two flavors
• 1xEV-DO for data only
• 1xEV-DV for data and voice

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EDGE
EDGE (Enhanced Data rates for Global Evolution)

• Further upgrade to GSM
• Possible 3G (no 2.75G) replacement for GPRS
• Uses improved modulation to triple the data rate
  where reception is clear

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LTE
LTE (3GPP LTE Long Term Evolution)

• 3G upgrade to UMTS
• 3GPP third generation partnership project
• LTE actually an architecture contains EPS
  (evolved packet system), EUTRAN (evolved UTRAN),
  and EPC (evolved packet core)
• OFDM, QPSK, 16QAM, 64QAM, MIMO

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16-2 SATELLITE NETWORKS
A satellite network is a combination of nodes,
some of which are satellites, that provides
communication from one point on the Earth to
another. A node in the network can be a
satellite, an Earth station, or an end-user
terminal or telephone.
Topics discussed in this section
OrbitsFootprint Three Categories of
Satellites GEO Satellites MEO Satellites LEO
Satellites
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Figure 16.13 Satellite orbits
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Example 16.1
What is the period of the Moon, according to
Keplers law?
Here C is a constant approximately equal to
1/100. The period is in seconds and the distance
in kilometers.
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Example 16.1 (continued)
Solution The Moon is located approximately
384,000 km above the Earth. The radius of the
Earth is 6378 km. Applying the formula, we get.
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Example 16.2
According to Keplers law, what is the period of
a satellite that is located at an orbit
approximately 35,786 km above the Earth?
Solution Applying the formula, we get
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Example 16.2 (continued)
This means that a satellite located at 35,786 km
has a period of 24 h, which is the same as the
rotation period of the Earth. A satellite like
this is said to be stationary to the Earth. The
orbit, as we will see, is called a geosynchronous
orbit.
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Table 16.1 Satellite frequency bands
L GPS S weather, NASA, Sirius/XM satellite
radio C open satellite communications Ku
popular with remote locations transmitting back
to TV studio Ka communications satellites
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Figure 16.15 Satellite orbit altitudes
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Figure 16.16 Satellites in geostationary orbit
Rotate with the earth, usually over equator 1/3
earth coverage
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Figure 16.16 Example GEO satellite Weather
Weather satellites can watch more than weather.
Can also observe city lights, fires, pollution
effects, auroras, sand and dust storms, snow
cover, energy flows, volcano output, etc. Can
observe both visible spectrum and infrared
spectrum The U.S. has two geostationary weather
birds GOES-11 and GOES-12. GOES-12, or
GOES-EAST, over the Mississippi River, covers
most of the U.S. weather. GOES-11 covers
the eastern Pacific Ocean.
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Figure 16.17 Orbits for typical LEO and MEO
systems, e.g. GPS
LEO and MEO satellites need to move or their
orbits will decay thus need gt1 satellite to
maintain connection.
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Figure 16.18 Trilateration
In a 2D plane, two reference points yields 2
intersections, three reference points yield 1
intersection In a 3D plane, need four reference
points to yield 1 intersection
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Figure 16.19 LEO satellite systems
UML user mobile link GWL gateway link ISL
intersatellite link
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Figure 16.20 LEO example Iridium constellation
Designed by Motorola during the 1990s,
went bankrupt in 1999. What cost 5 billion was
sold for 25 million. 66 active satellites with
a few spares at a height of 781 km (485 miles).
Sold to Iridium Communications Inc. Iridium
plans to send up 66 new satellites and 6
spares starting in 2015, called IridiumNext.
Data and voice.
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Figure 16.20 MEO example GPS (global
positioning system)
GPS was established in 1973 by U.S. and
consisted of 24 satellites (now 32). Dual-use
system military and civilian. Civilian side
used by commerce, science, banking,
mobile phones, farmers, surveyors, power grids,
you and me. GPS can provide absolute location,
relative movement, and time transfer. Inducted
into Space Foundation Space Technology Hall of
Fame in 1998. Three satellites gives you 2
points, but you can choose the one on the ground
4 gives you 1 point and overcomes clock errors
usually see at least 6 often see 8-10
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Figure 16.20 MEO example GPS (global
positioning system)
Each satellite continually transmits
messages that include (1) the time the message
was transmitted, (2) precise orbital information
(the ephemeris), and (3) general system health
and rough orbits of all GPS satellites (the
almanac) Receiver takes messages, determines the
transit time of each message and computes the
distances to each satellite. These distances
along with satellites locations are use in
determining receivers location
(trilateration). (See Wikipedia GPS for cool
image of satellite visibility.)
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Figure 16.20 MEO example GPS (global
positioning system)
GPS consists of 3 segments (1) Space segment
the space vehicles at 20,200km (2) Control
segment a master control station, an
alternate master control station, four dedicated
ground antennas, and six dedicated monitor
stations (3) User segment you and me All
satellites broadcast at two frequencies 1.57542
GHz and 1.2276 GHz using CDMA spread-spectrum
technology What will you create?