1. Mobile and Wireless Networking
Lecture 16 Dr. Xinbing Wang

2. Part 3: Current Wireless Systems
Cellular network architecture: UMTS (Chapter 10)
Mobile IP (Chapter 12)
Wireless LAN (Chapters 11/13/14)
Classification: Wireless LANs, PANs, and MANs
WiFi or IEEE
Network architecture, fact sheets, pros and cons
Physical medium
Protocol architecture: PCF and DCF
MAC: three methods, CSMA, DCF, and PCF
WiMAX or IEEE (Broadband Access)
In our daily lives, wireless communication technology is used everywhere, from VCR remote control, to satellite weather forecast. The common characteristics of wireless communication systems is that there is no physical (visible) lines between two communication parties.
Therefore, a wireless system is able to support user roaming. For example, we do not have to use a remote control in a particular position to.., we can use our cellular phones almost everywhere.
However, there are many impairments to a wireless channel, causing a lot of limitations to wireless communications system such as geographical.. (signal fading, additional noise, cochannel interference. Wireless systems also suffers from limit usable spectral width, so that the transmission rate is relatively low.
Specifically, wireless cellular systems based on radio propagation has been evolving from narrow band (1G, late 170s) to wide-band(3G).
With their geographical coverage limitation, wireless systems need a backbone network to extend their geographical coverage to enable global communications.
The interoworking of a wireless network as the front-end and the Internet as the backbone has received much attention in recent years.
So we will first take a look at the network architecture of current wireless systems,…, Then we will talk about the evolution from 2G to 3G systems.
Dr. Xinbing Wang

3. Method 3: DFWMAC-PCF (1)
The access mechanisms presented so far cannot guarantee a maximum access delay or minimum transmission bandwidth.
To provide a time bounded service, the standards specify a Point Coordination Function (PCF) on top of the DCF mechanisms.
Using PCF requires an access point that can controls medium access and polls the single nodes. Ad Hoc networks cannot use this function.
Dr. Xinbing Wang

4. Method 3: DFWMAC-PCF (2) t0 t1
SuperFrame
medium busy
PIFS
SIFS
SIFS D1 D2
point
coordinator
SIFS
SIFS U1 U2
wireless
stations
NAV
stations‘
NAV
At time t0 the contention-free period should start, but another station is transmitting data
After the medium has been idle, the PCF has to wait for PIFS before accessing the medium.
The point coordinator now sends data D1 to the first station. The station can answer after SIFS. After waiting for SIFS, the point coordinator can poll the second station by sending D2 (downstream).
The second station replies with U2 (upstream)
Dr. Xinbing Wang

5. Method 3: DFWMAC-PCF (3) t2 t3 t4
PIFS
SIFS D3 D4
CFend
point
coordinator
SIFS U4
wireless
stations
stations‘
NAV
NAV
contention free period t
contention
period
Polling continues with the third node which has nothing to answer.
After waiting for PIFS, the point coordinator can issue an end marker (CFend), indicating that the contention period may start again.
The cycle starts again with the next superframe
Dr. Xinbing Wang

6. 802.11 - Frame format Types Sequence numbers Addresses Miscellaneous
control frames, management frames, data frames
Sequence numbers
important against duplicated frames due to lost ACKs
Addresses
receiver, transmitter (physical), BSS identifier, sender (logical)
Miscellaneous
sending time, checksum, frame control, data
bytes 2 2 6 6 6 2 6
0-2312 4
Frame
Control
Duration/ ID
Address 1
Address 2
Address 3
Sequence
Control
Address 4
Data
CRC
bits 2 2 4 1 1 1 1 1 1 1 1
Protocol
version
Type
Subtype To DS
From DS
More
Frag
Retry
Power
Mgmt
More
Data
WEP
Order
Dr. Xinbing Wang

7. Special Frames: ACK, RTS, CTS
Acknowledgement
Request To Send
Clear To Send
bytes 2
Frame
Control 2
Duration 6
Receiver
Address 4
CRC
ACK
bytes 2 2 6 6 4
Frame
Control
Duration
Receiver
Address
Transmitter
Address
CRC
RTS
bytes 2 2 6 4
Frame
Control
Duration
Receiver
Address
CRC
CTS
Dr. Xinbing Wang

8. 802.11 - Roaming Scanning Reassociation Request Reassociation Response
scan the environment, i.e., listen into the medium for beacon signals or send probes into the medium and wait for an answer
Reassociation Request
station sends a request to one or several AP(s)
Reassociation Response
success: AP has answered, station can now participate
failure: continue scanning
AP accepts Reassociation Request
signal the new station to the distribution system
the distribution system updates its data base (i.e., location information)
typically, the distribution system now informs the old AP so it can release resources
Dr. Xinbing Wang

9. Part 3: Current Wireless Systems
Cellular network architecture: UMTS (Chapter 10)
Mobile IP (Chapter 12)
Wireless LAN (Chapters 11/13/14)
Classification: Wireless LANs, PANs, and MANs
WiFi or IEEE
Network architecture, fact sheets, pros and cons
Physical medium
Protocol architecture: PCF and DCF
MAC: three methods, CSMA, DCF, and PCF
WiMAX or IEEE (Broadband Access)
Wireless local loop (WLL) and Fixed Wireless Access (FWA)
service
WiMAX
In our daily lives, wireless communication technology is used everywhere, from VCR remote control, to satellite weather forecast. The common characteristics of wireless communication systems is that there is no physical (visible) lines between two communication parties.
Therefore, a wireless system is able to support user roaming. For example, we do not have to use a remote control in a particular position to.., we can use our cellular phones almost everywhere.
However, there are many impairments to a wireless channel, causing a lot of limitations to wireless communications system such as geographical.. (signal fading, additional noise, cochannel interference. Wireless systems also suffers from limit usable spectral width, so that the transmission rate is relatively low.
Specifically, wireless cellular systems based on radio propagation has been evolving from narrow band (1G, late 170s) to wide-band(3G).
With their geographical coverage limitation, wireless systems need a backbone network to extend their geographical coverage to enable global communications.
The interoworking of a wireless network as the front-end and the Internet as the backbone has received much attention in recent years.
So we will first take a look at the network architecture of current wireless systems,…, Then we will talk about the evolution from 2G to 3G systems.
Dr. Xinbing Wang

10. Wireless Local Loop (WLL)
Wired technologies responding to need for reliable, high-speed access by residential, business, and government subscribers
ISDN, xDSL, cable modems
Increasing interest shown in competing wireless technologies for subscriber access
Wireless local loop (WLL)
Narrowband – offers a replacement for existing telephony services
Broadband – provides high-speed two-way voice and data service
Dr. Xinbing Wang

11. WLL Configuration
Dr. Xinbing Wang

12. Advantages of WLL over Wired Approach
Cost – wireless systems are less expensive due to cost of cable installation that’s avoided
Installation time – WLL systems can be installed in a small fraction of the time required for a new wired system
Selective installation – radio units installed for subscribers who want service at a given time
With a wired system, cable is laid out in anticipation of serving every subscriber in a given area
Dr. Xinbing Wang

13. Propagation Considerations for WLL
Most high-speed WLL schemes use millimeter wave frequencies (10 GHz to about 300 GHz)
There are wide unused frequency bands available above 25 GHz
At these high frequencies, wide channel bandwidths can be used, providing high data rates
Small size transceivers and adaptive antenna arrays can be used
Dr. Xinbing Wang

14. Propagation Considerations for WLL
Millimeter wave systems have some undesirable propagation characteristics
Free space loss increases with the square of the frequency; losses are much higher in millimeter wave range
Above 10 GHz, attenuation effects due to rainfall and atmospheric or gaseous absorption are large
Multipath losses can be quite high
Dr. Xinbing Wang

15. 802.16 Standards Development
Use wireless links with microwave or millimeter wave radios
Use licensed spectrum
Are metropolitan in scale
Provide public network service to fee-paying customers
Use point-to-multipoint architecture with stationary rooftop or tower-mounted antennas
Provide efficient transport of heterogeneous traffic supporting quality of service (QoS)
Are capable of broadband transmissions (>2 Mbps)
Dr. Xinbing Wang

16. IEEE 802.16 Protocol Architecture
Dr. Xinbing Wang

17. Protocol Architecture: PHY and MAC
Physical and transmission layer functions:
Encoding/decoding of signals
Preamble generation/removal
Bit transmission/reception
Medium access control layer functions:
On transmission, assemble data into a frame with address and error detection fields
On reception, disassemble frame, and perform address recognition and error detection
Govern access to the wireless transmission medium
Dr. Xinbing Wang

18. Protocol Architecture: Convergence
Convergence layer functions:
Encapsulate PDU framing of upper layers into native MAC/PHY frames
Map upper layer’s addresses into addresses
Translate upper layer QoS parameters into native MAC format
Adapt time dependencies of upper layer traffic into equivalent MAC service
Dr. Xinbing Wang

19. IEEE 802.16 Services 802.16.1 802.16.3 Digital audio/video multicast
Digital telephony
ATM
Internet protocol
Bridged LAN
Back-haul
Frame relay
Voice transport
Data transport
Dr. Xinbing Wang

20. WiMAX Forum
The WiMAX mission is to make the interoperable. Just like WiFi did for
No WiMAX compliant products today, foreseen during The first WiMAX products will be based on d.
Intel is the most powerful player in WiMAX forum
Architecture specification work initiated in a new sub-group
No single global spectrum assigned, possibilites:
5.8 GHz, 3.5 GHz, 2.5 GHz, (IMT-2000 more likely in this band), and 2.3 GHz
Dr. Xinbing Wang

21. WiMAX Standards Roadmaps
WiMAX = interoperable subset of this (< 6 GHz)
Some Mobility
2005 ?
802.16e
Similar to .16a
Errata
Jul 2004
802.16d
2 – 11 GHz
NLOS
Jan 2003
802.16a
802.16
10 – 66 GHz
LOS
Sep 2000
NOTE: IEEE specifies only layer 1 & 2
Dr. Xinbing Wang

22. Applications of
Dr. Xinbing Wang

23. WiMAX Segments, High Level Pros and Cons
Backhaul, Fixed, point to point – LOS
High Bitrate
Low Interference
Clear Signal – No multipath fading
Relatively Low Cost
DSL, Fixed up to portable, Point to point, point to multipoint – NLOS
Relative high bitrate, but lower
One cell
Still relative cheap
Low to moderate interference-> Static radio environment
WAN and Mobile environment
Significantly lower bitrate
High interference. More multipath fading and dopplershift effects
Dr. Xinbing Wang

24. IEEE 802.16 Standards 802.16 802.16d/HiperMAN 802.16e Completed
WiMAX
802.16
802.16d/HiperMAN
802.16e
Completed
December 2001
June 2004 (802.16d)
Estimate 2005
Spectrum
GHz
< 11 GHz
< 6 GHz
Channel Conditions
Line of Sight Only
Non Line of Sight
Bit Rate
32 – 134 Mbps in 28MHz channel bandwidth
Up to 75 Mbps in 20MHz channel bandwidth
Up to 15 Mbps in 5MHz channel bandwidth
Modulation
QPSK, 16QAM and 64QAM
OFDM 256 FFT
QPSK, 16QAM, 64QAM
Scalable OFDMA
128 to 2048 FFT
Mobility
Fixed
Portable
Channel Bandwidths
20, 25 and 28 MHz
1.75 to 20 MHz
Dr. Xinbing Wang

25. Relation to Other Technologies
Whether a will complement or clash with certain other technologies remains to be seen. For a while, at least, it will certainly be complementary to a, enabling Wi-Fi users to dramatically extend their distance from wired networks.
Dr. Xinbing Wang

26. Theoretical WiMAX Raw Bandwidth (Mbit/s)*
Modulation /
Code rate
1,75 MHz
3,5 MHz
7,0MHz
14,0 MHz
20,0 MHz
1.45
2.91
5.82
11.64
16.26
QPSK 1/2
QPSK 3/4
2.18
4.36
8.73
17.45
24.40
34.91
48.79
16 QAM 3/4
16 QAM 1/2
23.27
32.53
64 QAM 2/3
64 QAM 3/4
46.55
65.05
6.55
13.09
26.18
52.36
73.19
*OFDM 256 FFT. Includes MAC and preamble overhead
Dr. Xinbing Wang

27. Theoretical Coverage (Km)*
Type of Area
Rooftop
Antenna
Window/Fixed
Antenna
Indoor/Portable
Antenna
Rural
<20 Km using
NLOS**
<8 Km
<4 Km
Suburban
N/A
<4 Km
<2 Km
Urban
N/A
<2 Km
<1 Km
*Approximate distances only, depends heavily on geographical area
**<50 Km is the theoretical maximum for LOS. Assumption is a NLOS base station and a rooftop antenna for better reception and maximum uplink power
Dr. Xinbing Wang

28. Portability (Mobility) in 802.16e
New network reference model
New BS-BS interface (IB) and BS-server interface (A) defined, mobile subscriber station (MSS)
Authentication and service authorization (ASA) servers provide authorization, authentication, billing, management, provisioning and other services. EAP is defined for SIM cards, and other means of Authentication (Extensible Auth. Protocol).
Dr. Xinbing Wang

29. Mobility in e – Layer 2
Handover (HO) process defined in MAC including
cell reselection
target BS scanning
network re-entry
HO decision and initiation and HO cancellation.
MAC messages for each of the handover functions defined.
Broadcast paging message defined.
Neighbor topology advertisement messages defined.
Option of using mobile IP provided.
Full QoS supported. All four GSM/WCDMA classes.
Dr. Xinbing Wang

30. Some Differences with 802.11 MAC OFDM Spectrum
802.11: Contention-based MAC (CSMA/CA), basically wireless Ethernet.
802.16: Dynamic TDMA-based MAC with on-demand bandwidth allocation.
OFDM
802.11a: 64 FTTs
802.16d: 256 FFTs
Spectrum
802.11: limited channels in Un-license spectrum
802.16: multiple channels in licensed & Un-license spectrum
Dr. Xinbing Wang

31. CPE: Customer Premise Chips
Comparison and
Technology
Range
Coverage
Data rate
Scalability
QOS
802.11
< 300 feet
Optimized for
indoor short range
2.7 bps/Hz peak.
<= 54Mbps in 20MHz
1-10 CPE CSMA/CA
No QOS
802.16
< 30 Mile ( typical 3~4)
Outdoor LOS & NLOS
5bps/Hz peak,
<100Mbps in 20 MHz
1- hundreds CPE TDMA
On demand BW  voice
Video, data
CPE: Customer Premise Chips
Dr. Xinbing Wang

32. Broadband Wireless Systems
WiMAX
Wireless Broadband
Laptop centric
Fixed  Portability
Line-of-Sight & Non Line-of-Sight
IEEE Layer 1 & 2 standard
Data optimized
Optimized for Fixed High data rate
Evolution towards mobility
Drivers:
Data optimized network (simple)
DSL complement
3G Evolved
Mobile Broadband
Phone & laptop
Full mobility
Non line-of-sight
3GPP and 3GPP2 standard
Voice/data optimized
Optimized for Mobility
Evolution towards Higher Data
Drivers:
Mobile Broadband for incremental investment
National & global roaming networks
Dr. Xinbing Wang

33. Peak Bit Rates Comparison
Channel
Bandwidth
FDD/TDD
Peak
bit-rate DL
Peak
Bit-rate UL
Standards
compliant
GSM/GPRS
3GPP
FDD
160 kbps
160 kbps
200KHz
EDGE
FDD
480 kbps
480 kbps
3GPP
WCDMA
FDD/TDD
2 Mbps
2 Mbps
3GPP
5Mhz
HSDPA
FDD
14.4 Mbps
7.68 Mbps
3GPP
CDMA2000 1x
FDD
640 kbps
450 kbps
3GPP2
1xEV-DO
1.25 MHz
FDD
3.1 Mbps
1.8 Mbps
3GPP2
1xEV-DV
FDD
3.1 Mbps
1.8 Mbps
3GPP2
IEEE d
-20 MHz
FDD/TDD
- 75 Mbps
- 75 Mbps
IEEE _
Flarion
1.25 MHz
FDD
3.2 Mbps
900 kbps
Dr. Xinbing Wang

34. Summary Cellular network architecture: UMTS (Chapter 10)
Mobile IP (Chapter 12)
Wireless LAN (Chapters 11/13/14)
Classification: Wireless LANs, PANs, and MANs
WiFi or IEEE
Network architecture, fact sheets, pros and cons
Physical medium
Protocol architecture: PCF and DCF
MAC: three methods, CSMA, DCF, and PCF
WiMAX or IEEE (Broadband Access)
Wireless local loop (WLL) and Fixed Wireless Access (FWA)
services
WiMAX
Reading materials: http: //
Dr. Xinbing Wang