A Tale of Two Technologies: A Tale of Two Technologies:

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1
A Tale of Two Technologies:
A Tale of Two Technologies:
Lecture #2
A Tale of Two Technologies:
A Tale of Two Technologies:
WiMAX vs. LTE
WiMAX vs. LTE
Dr. Kun Yang
Universit
y
of Essex, UK
1
y
17
th
March 2009 @ NII
Agenda
Wireless LAN (Local Area Networks)
Wireless MAN: WiMAX
Mobile Cellular Systems
3GPP LTE (Long Term Evolution)
Femto Cell and Mobility
2
Q&A
Some slides here pay courtesy to J. He, & D. Hunter.
2
IEEE 802 (LAN) vs OSI

IEEE 802 reference model

Lower layers of OSI model

Physical

Media access control (MAC)

Logical link control (LLC)

IEEE 802 11
3
IEEE

802
.
11
•IEEE 802.15
•IEEE 802.16
•IEEE 802.21
IEEE 802.11 Version Summary
4
3
Comparison: infrastructure vs. ad-hoc
networks
infrastructure
network
ad
hoc network
AP
AP
AP
wired network
AP: Access Point
5
ad
-
hoc

network
802.x LAN
802.11 LAN
802.11 - Architecture of an
infrastructure network
Station (STA)

terminal with access mechanisms
to the wireless medium and radio
contact to the access point
STA
1
Distribution System
Portal
Access
Point
BSS
BSS
1
Access
Point
contact to the access point
Basic Service Set (BSS)

group of stations using the same
radio frequency
Access Point

station integrated into the wireless
LAN and the distribution system
Portal
ESS
6
802.11 LAN
BSS
2
Portal

bridge to other (wired) networks
Distribution System

interconnection network to form
one logical network (EES:
Extended Service Set) based
on several BSS
STA
2
STA
3
4
802.11 - Architecture of an ad-hoc network
Direct communication
within a limited ran
g
e
802.11 LAN
STA
1
g

Station (STA):
terminal with access
mechanisms to the
wireless medium

Basic Service Set (BSS):
group of stations using the
same radio frequency
BSS
BSS
1
STA
1
STA
2
STA
3
7
802.11 LAN
BSS
2
STA
4
STA
5
ETSI - HIPERLAN
ETSI standard

European standard, cf. GSM, DECT, ...

Enhancement of local Networks and interworking with fixed networks

integration of time
-
sensitive services from the early beginning

integration of time
-
sensitive services from the early beginning
HIPERLAN family

one standard cannot satisfy all requirements
• range, bandwidth, QoS support
• commercial constraints

HIPERLAN 1 standardized since 1996
medium access
network layer
higher layers
lo
g
ical link
8
physical layer
channel access
control layer
control layer
physical layer
data link layer
HIPERLAN layers OSI layers
network

layer
physical layer
medium access
control layer
g
control layer
IEEE 802.x layers
5
802.11 - MAC layer I - DFWMAC
Traffic services

Asynchronous Data Service (mandatory)
• exchange of data packets based on “best-effort”
f b d d l i
• support

o
f b
roa
d
cast

an
d
mu
l
t
i
cast

Time-Bounded Service (optional)
• implemented using PCF (Point Coordination Function)
Access methods

DFWMAC-DCF CSMA/CA (mandatory)
• collision avoidance via randomized „back-off“ mechanism
• minimum distance between consecutive packets

ACK packet for acknowledgements (not for broadcasts)
9

ACK packet for acknowledgements (not for broadcasts)

DFWMAC-DCF w/ RTS/CTS (optional)
• Distributed Foundation Wireless MAC
• avoids hidden terminal problem

DFWMAC- PCF (optional)
• access point polls terminals according to a list
802.11 - MAC layer II
Priorities

defined through different inter frame spaces (IFS)

no guaranteed, hard priorities
SIFS (Sh t I t F S i )

SIFS (Sh
or
t I
n
t
er
F
rame
S
pac
i
n
g)
• highest priority, for ACK, CTS, polling response

PIFS (PCF IFS)
• medium priority, for time-bounded service using PCF

DIFS (DCF, Distributed Coordination Function IFS)
• lowest priority, for asynchronous data service
DIFS
DIFS
10
t
medium busy
SIFS
PIFS
DIFS
DIFS
next frame
contention
direct access if
medium is free ≥ DIFS
6
DIFS
DIFS
contention window
(randomized back-off
mechanism)
802.11 - CSMA/CA access method I
t
medium busy
next frame

station ready to send starts sensing the medium (Carrier
Sense based on CCA, Clear Channel Assessment)

if the medium is free for the duration of an Inter-Frame
S
p
ace
(
IFS
)
, the station can start sendin
g

(
IFS de
p
ends on
slot time
direct access if
medium is free ≥ DIFS
11
p ( ) g ( p
service type)

if the medium is busy, the station has to wait for a free IFS,
then the station must additionally wait a random back-off
time (collision avoidance, multiple of slot-time)

if another station occupies the medium during the back-off
time of the station, the back-off timer stops (fairness)
802.11 - competing stations - simple version
station
1
DIFS
bo
e
bo
r
DIFS
bo
e
bo
r
DIFS
DIFS
bo
e
busy
busy
station
2
station
3
station
4
t ti
bo
e
bo
e
bus
y
bo
r
bo
e
bo
e
busy
busy
bo
e
bo
e
bo
r
bo
r
12
t
bo
e
s
t
a
ti
on
5
packet arrival at MAC
elapsed backoff time
bo
r
residual backoff time
busy
medium not idle (frame, ack etc.)
7
802.11 - CSMA/CA access method II
Sending unicast packets

station has to wait for DIFS before sending data

receivers acknowled
g
e at once
(
after waitin
g
for SIFS
)
if the
g ( g )
packet was received correctly (CRC)

automatic retransmission of data packets in case of
transmission errors
SIFS
DIFS
C
sender
data
13
t
data
A
C
K
waiting time
other
stations
receiver
DIFS
contention
802.11 - DFWMAC
Sending unicast packets

station can send RTS with reservation parameter after waiting for DIFS
(reservation determines amount of time the data packet needs the medium)

acknowled
g
ement via CTS after SIFS b
y
receiver (if read
y
to receive)

sender can now send data at once, acknowledgement via ACK

other stations store medium reservations distributed via RTS and CTS
SIFS
DIFS
ACK
receive
r
sender
data
RTS
CTS
SIFS
SIFS
14
t
data
defer access
other
stations
DIFS
contention
NAV (RTS)
NAV (CTS)
8
Fragmentation
DIFS
f
RTS
f
t
SIFS
data
ACK
1
other
stations
receiver
sender
f
rag
1
DIFS
RTS
CTS
SIFS
SIFS
NAV (RTS)
NAV (CTS)
NAV (frag
1
)
NAV (ACK
1
)
SIFS
ACK
2
f
rag
2
SIFS
15
t
contention
DFWMAC-PCF I
SuperFrame
t
0
di b
t
1
PIFS
stations‘
NAV
wireless
stations
point
coordinator
D
1
U
1
SIFS
NAV
SIFS
D
2
U
2
SIFS
SIFS
me
di
um
b
us
y
16
At the beginning of the contention-free period, the AP transmits a beacon
frame (not shown above –see later)

This announces the maximum duration of the contention-free period

All stations use this duration to set their NAVs
9
DFWMAC-PCF II
t
2
t
3
t
4
t
stations‘
NAV
wireless
stations
point
coordinator
D
3
NAV
PIFS
D
4
U
4
SIFS
SIFS
CF
end
contention
contention free period
17
period
802.11 - Frame format
Types

control frames, management frames, data frames
Se
q
uence numbers
q

important against duplicated frames due to lost ACKs
Addresses

receiver, transmitter (physical), BSS identifier, sender (logical)
Miscellaneous

sending time, checksum, frame control, data
2
2 6 6 6 62 40-2312
bytes
18
Frame
Control
Duration
ID
Address
1
Address
2
Address
3
Sequence
Control
Address
4
Data
CRC
version, type, fragmentation, security, ...
10
MAC address format
scenario
to DS
from
DS
address 1
address 2
address 3
address 4
ad-hoc network
0
0
DA
SA
BSSID
-
i f t t
0
1
DA
BSSID
SA
i
n
f
ras
t
ruc
t
ure
network, from AP
0
1
DA
BSSID
SA
-
infrastructure
network, to AP
1
0
BSSID
SA
DA
-
infrastructure
network, within DS
1
1
RA
TA
DA
SA
DS: Distribution System
AP: Access Point
DA:Destination Address
19
DA:

Destination

Address
SA: Source Address
BSSID: Basic Service Set Identifier
RA: Receiver Address
TA: Transmitter Address
802.11 - MAC management
Synchronization

try to find a LAN, try to stay within a LAN
i

t
i
mer

etc.
Power management

sleep-mode without missing a message

periodic sleep, frame buffering, traffic measurements
Association/Reassociation

integration into a LAN
20

roamin
g
, i.e. chan
g
e networks b
y
chan
g
in
g
access points

scanning, i.e. active search for a network
MIB - Management Information Base

managing, read, write
11
A bit info on MANET (Mobile Ad hoc
Networks) ….
21
MANET Introduction
Mobile ad hoc networks (MANETs) are basically peer-to-peer
multihop mobile wireless networks that

have neither fixed communication infrastructure

nor any base stations (BSs)
nor any base stations (BSs)
.

Control is more complex due to its ad hoc nature and mobility.

Unlike the typical Internet, which has dedicated nodes for basic
network operations such as authorization, routing, packet forwarding,
and network management, all these functions should be performed by
all MNs themselves in MANETs.
Efficient routing of packets is a primary MANET challenge.
M
A
N
ET
s use
m
u
l
t
ih
op
r
at
h
e
r
t
h
a
n
s
in
g
l
e
-h
op
r
out
in
g
to de
li
ve
r

22
M N s use u t op at e t a s g e
op
out g
to de ve
packets to their destination.
12
Routing
Conventional networks typically rely on distance-vector or link-
state algorithms, which depend on periodic broadcast
advertisements of all routers to keep routing tables up-to-date.
I MANET l th l ith hi h
I
n

some

cases,
MANET
s

a
l
so

use
th
ese

a
lg
or
ith
ms,

w
hi
c
h
ensure

that the route to every host is always known.
However, this approach presents several problems:

periodically updating the network topology increases bandwidth
overhead;

repeatedly awakening hosts to receive and send information quickly
exhausts batteries;

the propagation of routing information which depends on the
23

the propagation of routing information
,
which depends on the
number of existing hosts, causes overloading, thereby reducing
scalability;

redundant routes accumulate needlessly;

communication systems often cannot respond to dynamic changes in
the network topology quickly enough.
On-demand Routing Algorithms
Rather than relying on periodical broadcasts of
available routes, called
p
roactive, a re-active al
g
orithm
p
g
discovers routes is needed.
Because the route to every mobile node is not known at
any given time, these algorithms must build and
maintain routes.
Two representative MANET re-active algorithms:

DSR: data source routin
g
24
g

AODV: ad-hoc distance vector
13
Bluetooth
Why Bluetooth

1994 – Ericsson study on a wireless technology to link mobile
phones and accessories
phones and accessories

Lets replace all those ugly wires with a short range low data
rate wireless system.

Basically to standardise wireless keyboards and mice
• And add a few more on the way
25
Main references:

IEEE Std 802.15.1, “Information Technology —Telecommunications and
Information Exchange between Systems —Local and Metropolitan Area
Networks —Specific Requirements Part 15.1: Wireless Medium Access
Control (MAC) and Physical Layer (PHY) Specifications for Wireless
Personal Area Networks (WPANs),” 2002.
Bluetooth
Bluetooth is a standard for wireless communications.
Bluetooth is an infrastructure less short-range wireless
d d l h bl b l
s
y
stem inten
d
e
d
to rep
l
ace t
h
e ca
bl
e
b
etween e
l
ectronic
user terminals with RF links.
The devices can also be used for communications
between portable computers, act as bridges between
other networks, or serve as nodes of ad hoc networks.
This range of applications is known as wireless personal
26
area network (WPAN).
Bluetooth devices use the 2.4 GHz band, which is
unlicensed in most countries.
14
Piconet
The Bluetooth topology is a star network where a master node can
have up to seven slave nodes wirelessly connected to it to form a
piconet.
Pi t
i th i l t fi ti f Bl t th t k
Pi
cone
t
i
s
th
e

s
i
mp
l
es
t
con
fig
ura
ti
on

o
f
a
Bl
ue
t
oo
th
ne
t
wor
k
.
Each piconet uses a centrally assigned time-division multiple
access (TDMA) schedule and frequency hopping pattern.
Transmission power is typically around 20 dBm and the
transmission range is on the order of tens of meters.
27
Scatternet
Piconets may be connected together, thus forming a scatternet.
A scatternet supports multihop.

i.e., two nodes can communicate with each other even if there is no
direct connection between them by using other nodes as relays
direct connection between them by using other nodes as relays
.

Two piconets can communicate by means of a common node
belonging to both of them. A node can be a master in one piconet
at most and a slave in several others.
28
15
Bluetooth vs. IEEE 802.11 (1)
29
Bluetooth vs. IEEE 802.11 (2)
30
16
Agenda
Wireless LAN (Local Area Networks)
Wireless MAN: WiMAX (IEEE 802.16)

WiMAX PHY/MAC/QoS Features

Comparison with IEEE 802.11
Mobile Cellular Systems
31
3GPP LTE (Lon
g
Term Evolution)
Femto Cell and Mobility
Q&A
IEEE 802.16
WiMAX is the commercialization of the IEEE 802.16 standard,

Started at the National Institute of Standards and Technologies (NIST) in
1998 and then transferred to the IEEE to form Working Group 802.16.
h k l f h l

In June 2004, t
h
e wor
k
in
g

g
roup won approva
l

f
or t
h
e
l
atest 802.16
standard for fixed wireless access, known as IEEE 802.16-2004.

In December 2005, an extension that addresses mobility also won approval
as IEEE 802.16e-2005.
Specifies the air interface, including the medium access control layer
(MAC) and physical layer (PHY), of fixed point-to-multipoint (PMP)
and Mesh broadband wireless access systems providing multiple
services
32
services
.

The standard includes a particular physical layer specification broadly
applicable to systems operating between 10 and 66 GHz, and below
10GHz.
WiMAX: Worldwide Inter-operability for Microwave Access
17
The WiMAX Forum
Comprises a group of industry leaders (Intel, AT&T, Samsung,
Motorola, Cisco, and others), has closely supported and promoted
the technology.
The
g
roup’s workforce is divided alon
g
multiple workin
g

g
roups
that focus on technical, regulatory, and marketing aspects.
Loads of live discussion about technical details of WiMAX and its
simulation and implementation.
High Performance Radio Metropolitan Area Network
(
Hi
p
erMAN
)
, the Euro
p
ean Telecommunications Standards
33
(
p
) p
Institute’s MAN standard, share the same physical layer (PHY)
and medium access control (MAC) layer specifications.
Standard History

Original fixed wireless broadband air Interface for 10 – 66 
GHz:Line

of

sight only,Point

to

Multi

Point applications
• First standard based on proprietary implementations of DOCSIS/HFC       
architecture in wireless domain
802.16
(Dec 2001)

Extension for 2‐11 GHz: Targeted for non‐line‐of‐sight, 
Point‐to‐Multi‐Point applications like “last mile” 
broadband access
GHz:
 
Line
of
sight
 
only,
 
Point
to
Multi
Point
 
applications

802.16 Amendment WiMAX System Profiles 10 ‐ 66 GHz, 
line‐of‐sight
(Dec

2001)
802.16c
(2002)
802.16a
(Jan 2003)
34

Adds WiMAX System Profiles and Errata for 2‐11 GHz

MAC/PHY Enhancements to support subscribers 
moving at vehicular speeds
802.16d
(802.16-2004)
(Oct 2004)
802.16e
(802.16-2005)
(Dec 2005)
18
Other versions
802.16f-2005 —Management Information Base (MIB)
802.16g-2007 —Management Plane Procedures and Services
802 16k
2007
Bridging of 802 16 (an amendment to 802 1D)
802
.
16k
-
2007

Bridging of 802
.
16 (an amendment to 802
.
1D)
802.16h —Improved Coexistence Mechanisms for License-Exempt
Operation
802.16i —Mobile Management Information Base
802.16j —Multihop Relay Specification
802.16Rev2 —Consolidate 802.16-2004, 802.16e, 802.16f, 802.16g
and possibly 802.16i into a new document.
35
802.16m —Advanced Air Interface. Data rates of 100 Mbit/s for
mobile applications and 1 Gbit/s for fixed applications.
Source: wikipedia
Services
Deliver both fixed and mobile wireless broadband services
Two forms of wireless service:

Desirable Non-line-of-sight (NLOS) service
• Small antenna
• 2 – 11 GHz
• Up to 8 km radius (cell phone zone)

Line-of-sight (LOS)
• Fixed antenna; strong and stable connection
• 10 – 66 GHz
• Up to 50 km radius
Applications
B db d
d d
36

B
roa
db
an
d
o
n
-
d
eman
d
• Fast deployment of WLAN hotspots

Residential broadband
• Hard competition with DSL, cable and fiber

Cellular Backhaul

Underserved areas

Emergency communication systems
19
Reference Model
37
Protocol Stack
Upper
Layers
Service specific convergence sublayer
MAC sublayer common part
Security sublayer
Transmission convergence sublayer
Data Link
Layer
38
Physical medium dependent sublayer
(QPSK | QAM-16 | QAM-64)
Physical
Layer
20
PHY Considerations
Broadband channels

Wide channels
(
20, 25, or 28 MHz
)
( )

High capacity – Downlink AND Uplink
Multiple access

TDM/TDMA

High rate burst modems
Adaptive burst profiles on uplink and downlink
Duplex scheme
39
Duplex scheme

Time-Division Duplex (TDD)

Frequency-Division Duplex (FDD) [including Burst FDD]
Support for half-duplex terminals (cheaper)
Adaptive PHY
Channel
Width
Symbol
Rate
(M/)
Bitrate (Mbit/s) Num. of PSs
(Phy. slots)
QPSK 16- 64-QAM
40
(MHz)
(M
s
y
m
/
s
)
(1ms frame)
QAM
20 16 32 64 96 4000
25 20 40 80 120 5000
28 22.4 44.8 89.6 134.4 5600
21
Adaptive Burst Profiles
Burst profile

Set of parameters that describe the uplink or downlink
transmission properties associated with an interval usage code
transmission properties associated with an interval usage code
(IUC)

Each profile contains parameters such as modulation type, forward
error correction (FEC) type, preamble length, guard time, etc.
Dynamically assigned according to link conditions

Burst by burst, per subscriber station

Trade-off between ca
p
acit
y
vs. robustness in real time
41
p y
Burst profile for downlink broadcast channel is well known

All other burst profiles could be configured “on the fly”
TDD Frame
42
Frame duration: 1 ms    Physical Slot (PS) = 4 symbols
22
TDD Downlink Subframe
43
DIUC: Downlink Interval Usage Code
TTG: Transmit Transition Gap
Burst FDD Frame
44
23
FDD Downlink Subframe
45
TDMA portion: transmits data to some half-duplex
SSs (the ones scheduled to transmit earlier in the
frame than they receive). Need preamble to re-
sync (carrier phase)
Typical Uplink Subframe (TDD or FDD)
SSTG : Subscriber Station Transition Gap
UIUC: Uplink Interval Usage Code
46
24
Air Interfaces Specifications
Designation Applicability MAC Duplexing
WirelessMAN-SC 10-66 GHz
License
d
Basic TDD, FDD,
HFDD
WirelessMAN-SCa 2-11 GHz
Licensed
Basic, (ARQ),
(STC), (AAS)
TDD, FDD
WirelessMAN-
OFDM
2-11 GHz
Licensed
Basic, (ARQ),
(STC), (AAS)
TDD, FDD
2-11 GHz License-
exempt
Basic, (ARQ),
(STC), (DFS),
(MSH), (AAS)
TDD
47
WirelessMAN-
OFDMA
2-11 GHz
Licensed
Basic, (ARQ),
(STC), (AAS)
TDD, FDD
2-11 GHz License-
exempt
Basic, (ARQ),
(STC), (DFS),
(MSH), (AAS)
TDD
MAC Requirements
Provide Network Access
Address the Wireless environment

e.
g
., ver
y
efficient use of spectrum
Broadband services

Very high bit rates, downlink and uplink

A range of QoS requirements

Convergence layers to ATM, IP, Ethernet, ...
Likelihood of terminal being shared
48

Base Station may be heavily loaded
Security
Support PHY alternatives

Adaptive mod, TDD/FDD; single-carrier, OFDM/OFDMA, etc.
25
MAC layer architecture
MAC
IP/Ethernet/VLAN
Packet convergence sub‐layer
(classify, connection, QoS, 
ATM
ATM convergence sub‐layer
(classify, connection, QoS, 
Layer
b
andwidth allocation)
b
andwidth allocation)
Basic 
connection
(RLC and short, 
Time‐critical 
MAC msg)
Primary 
connection
(authentication,
Connection 
setup)
Secondary 
connection
(DHCP, TFTP, 
SNMP..)
Traffic 
connection
(data)
Other connects
(Initial access
Broadcast
Multicast)
Grant management subheader
Fragmentation
subheader
Packing
subheader
MAC (G i b d idth t) H d (6 b t 48 bit )
Mesh subheader
Management connections
49
MAC
 
(G
ener
i
c or 
b
an
d
w
idth
 reques
t)
 
H
ea
d
er 
(6
 
b
y
t
es=
48
 
bit
s
)
Transmission Convergence sub‐layer 
PHY
10‐66 GHz
PHY
2‐11 GHz
Basic connection:
short, time-urgent msg
Primary connection:
Long, delay-tolerant msg
Secondary connection:
Delay-tolerant standard-based msg
QoS Support
QoS support is critical for the support of commercial
applications
f l f d h
De
f
ines 4+1 c
l
ass o
f
services, associate
d
wit
h
connections
– ref. next slide
Scheduling Services Parameters

Maximum sustained traffic rate

Minimum reserved traffic rate

Maximum latency
50

Tolerated
j
itter

Traffic priority

Request/transmission policy
Bandwidth request and grant mechanisms
26
Classes of Service
Unsolicited Grant Services (UGS)

for constant bit-rate (CBR) or CBR-like service flows (SFs), e.g.
T1/E1
T1/E1
Real-time Polling Services (rtPS)

for rt-VBR-like SFs such as MPEG video
Non-real-time Polling Services (nrtPS)

for nrt SFs with better than best effort service such as bandwidth-
intensive file transfer
B t Eff t (BE)
51
B
es
t Eff
or
t (BE)

for best-effort traffic
Mandatory QoS service flow parameters

Maximum sustained traffic rate (MSTR)

Minimum reserved traffic rate (MRTR)

Maximum latency (ML)

Maximum latency (ML)

Tolerated jitter (TJ)

Traffic priority (TP)

Request/transmission policy (RTP)
Service MSTR MRTR ML TJ TP RTP
UGS Yes Optional Yes Yes No Yes
52
rtPS Yes Yes Yes No No Yes
nrtPs Yes Yes No No Yes Yes
BE No No No No Yes Yes
27
Bandwidth Request and Allocation
SSs make bandwidth requests to the BS in many ways:

Implicit requests (UGS): No actual messages, negotiated at
connection setu
p
BS grants/allocates bandwidth in one of two modes:
p

Send a standalone MAC message called ”BW request” in an
allready granted slot (allocated via polling service).

Use the ”contention request opportunities” interval, e.g., upon being
polled by the BS (multicast or broadcast poll).

Piggyback a BW request message on a data packet.
53

Grant Per Subscriber Station (GPSS)

Grant Per Connection (GPC)
Decision based on requested bandwidth and QoS
requirements vs the available resources at BS.
Grants are realized through the UL-MAP.
Unicast Polling
1.
BS allocates space for the SS in
BS
SS
the uplink subframe (usin
g
UL-
MAP)
2.
SS uses the allocated space to
send a bw request.
3.
BS allocates the requested space
for the SS if available
(
usin
g
UL-
Poll
Request
Allocate
Data
BS
SS
54
( g
MAP
4.
SS uses allocated space to send
data.
scheduling
28
Agenda
Wireless LAN (Local Area Networks)
Wireless MAN: WiMAX (IEEE 802.16)

WiMAX PHY/MAC Features

Comparison with IEEE 802.11
Mobile Cellular Systems
55
3GPP LTE (Lon
g
Term Evolution)
Femto cell and Mobility
Q&A
UNII
ISM
802.11 vs. 802.16: Spectrum
International
Licensed
US
Licensed
Japan
Licensed
International
Licensed
ISM
802 16
GHz
1
3
2
4
5
802.11
802
.
16
56
ISM: Industrial, Scientific & Medical Band – Unlicensed band
U-NII: Unlicensed National Information Infrastructure – Unlicensed band,
by FCC, mainly for 802.11a.
802.16a has both licensed and license-exempt options
J. Orr of Proxim
29
Channel Performance
Channel
Bandwidth
Maximum
bps/Hz
Maximum
Data Rate
802.16a
~5.0 bps/Hz
~2.7 bps/Hz54 Mbps20 MHz
63 Mbps
10, 20 MHz;
1.75, 3.5, 7, 14 MHz;
3, 6 MHz
802.11a
Scalability:
802 11 MAC d i d t t 10’ f h
57
802.16 is designed for metropolitan performance
802
.
11
a
MAC d
es
ig
ne
d t
o

suppor
t 10’
s

o
f
users

w
h
ereas

802.16 to support thousands of users
J. Orr of Proxim
QoS
IEEE 802.11
IEEE 802.16a

Contention-based MAC

Grant-re
q
uest MAC
QoS
(CSMA/CA) => poor
performance under heavy load.

No guaranteed QoS

No differentiated service
on a per-user basis

TDD only – asymmetric
802 11 Q S i i iti ti
q

QoS mechanism is part of the
standard

Designed to support Voice
and Video

Supports 5
differentiated service
levels
58

802
.
11
e:
Q
o
S i
s

pr
i
or
iti
za
ti
on

only
levels

TDD/FDD – asymmetric
or symmetric

AMC: Adaptive Modulation
and Coding
30
802.11 802.16a
Optimized for ~100 meters
Optimized for up to 50 Km
Range
No “near-far” compensation
Designed to handle indoor multi-path
(delay spread of 0.8μ seconds),
optimized for indoor
Designed to handle many users spread out over
kilometers
Designed to tolerate greater
multi-path delay spread up to 10.0μ seconds,
optimized for outdoor NLOS performance
PHY d MAC d i d ith lti
il
59
Optimization centers around PHY
and MAC layer for 100m range
Range can be extended by increasing
trans. Power - may be non-standard
PHY
an
d MAC d
es
i
gne
d
w
ith
mu
lti
-m
il
e

range

in mind
Standard MAC
802.16a is designed for distance
802.11 and 802.16 both gain broader industry
acceptance through
conformance and
IEEE 802.11 vs 802.16: Summary
• 802.11 is mainly optimized for license-exempt LAN
operation
802 16 i i l ti i d f
li d
MAN
acceptance through
conformance and
interoperability by multiple vendors
802.16 complements
802.11 by creating a
complete MAN-LAN solution
60

802
.
16 i
s

ma
i
n
l
y

op
ti
m
i
ze
d f
or

li
cense
d
MAN
operation.
J. Orr of Proxim
31
Agenda
Wireless LAN (Local Area Networks)
Wireless MAN: WiMAX (IEEE 802.16)
Mobile Cellular Systems
3GPP LTE (Long Term Evolution)
Femto cell and Mobility
61
Q&A
Motivation
Radio spectrum is very limited,

we have only 10-25MHz dedicated to wireless communication.
h b d d h ll
h l f
Suc
h
narrow
b
an
d
wi
d
t
h
a
ll
ows 100-400 c
h
anne
l
s o
f

reasonable quality,

which is not rational and commercially not profitable to
develop network for such small number of mobile subscribers.
Then the cellular idea: division of the whole
geographical area to relatively small cells, and each cell
ma reuse the same frequencies b reducing power of
62
may reuse the same frequencies by reducing power of
transmission.
Each cell has its own antenna (base station), and all
base stations are interconnected using microwave or
cable communication.
32
A bit of history
Once upon a time there was analog cellular
communication

didn’t su
pp
ort encr
yp
tion, com
p
ression, and ISDN
pp yp p
compatibility;

in addition each country (company) developed its own system,
which was incompatible with everyone else’s in equipment
and operation.
So, in early 80s Europeans realized that pan-European
public mobile system should be developed. The new
system had to meet certain criteria:
63
system had to meet certain criteria:

Good subjective speech quality

Low terminal and service cost

International roaming

ISDN compatibility

Digital
Cellular Network Organization
Areas divided into cells

Each cell served by its own
base station consisting of
base

station

consisting

of

transmitter, receiver, and
control unit,

Cells set up such that
antennas of all neighbors are
equidistant (hexagonal
pattern)
64
33
Frequency Reuse
Adjacent cells are assigned different frequencies to
avoid interference or crosstalk
b f b ll
O
bj
ective is to reuse
f
requenc
y
in near
by
ce
ll
s

10 to 50 frequencies assigned to each cell

Transmission power controlled to limit power at that
frequency escaping to adjacent cells.

The issue is to determine how many cells must intervene
between two cells using the same frequency.
65
Examples
66
N=4
N=7
34
Frequency reuse
Reuse Distance (D): minimum distance between
centres of cells that use the same band of frequencies
(co-channels)
67
Increasing Capacity
Adding new channels
Frequency borrowing – frequencies are taken from
d ll b d ll
a
dj
acent ce
ll
s
by
con
g
este
d
ce
ll
s
Cell splitting – cells in areas of high usage can be split
into smaller cells
Cell sectoring – cells are divided into a number of
wedge-shaped sectors, each with their own set of
channels. Directional Antennas must be used in this case.
68
Microcells – a decrease in cell size results in a
reduction of the radiated power levels.
35
Example: Microcells
Area: 213 km
2 ,
Bandwidth: 336 channels per cluster, cells per
cluster: N=7

Number of channels per cell is 336/7=48
If cell radius R=1.6 km
,
then 32 total cells
,

Total channel capacity is 48 x 32 = 1536
If cell radius R=0.6 km, then 128 cells

Total channel capacity is 48 x128 =6144 channels
69
Total cells: 32 Total cells: 128
Architecture of the GSM system
GSM is a PLMN (Public Land Mobile Network)

several providers setup mobile networks following the GSM
standard within each country
standard within each country

components
• MS (mobile station)
• BS (base station)
• MSC (mobile switching center)
• LR (location register)

subsystems
• RSS (radio subsystem): covers all radio aspects
70
• NSS (network and switchin
g
subs
y
stem): call forwardin
g
,
handover, switching
• OSS (operation subsystem): management of the network
36
GSM: overview
fixed network
GMSC
HLR
NSS
OMC, EIR,
AUC
BSC
BSC
MSC
MSC
VLR
with OSS
VLR
71
RSS
radio
subsystem
MS
MS
network and
switching subsystem
fixed
partner networks
GSM: system architecture
U
m
A
bis
BTS
BSC
BTS
MSC
SS7
EIR
HLR
ISDN
PSTN
72
A
BSS
BTS
BSC
BTS
MSC
IWF
ISDN
PSTN
PSPDN
CSPDN
VLR
37
Agenda
Wireless LAN (Local Area Networks)
Wireless MAN: WiMAX (IEEE 802.16)
Mobile Cellular Systems
3GPP LTE (Long Term Evolution)
Comparison and Mobility
73
Q&A
Cellular Networks: Generations
Once upon a time there was analog cellular communication – 1
st
G
2
nd
Generation (2G): digital, early 80s, GSM
2.5G or GPRS: 140.8 kb/s in theory, 56 kb/s in practice
2.75G or E-GPRS or EDGE (Enhanced Data Rates for GSM
Evolution): 180 kbps effective
3G:

UMTS using WCDMA supports 14Mbps in theory. 384 kbps, or 3.6
Mbps for HSDPA handsets;
• O2, 3, Orange, AT&T, HK, Taiwan, etc.
• Different countries use diff. frequencies, thus diff. handsets

CDMA-2000: (2.5G+3G), e.g., China Unicom
74

TD-SCDMA at China; to avoid patent fees
3.5G: UMTS is being upgraded to High Speed Downlink Packet
Access (HSDPA): up to 7.2 Mb/s.
3.99G/4G: the 3GPP Long Term Evolution (LTE) project plans to
move UMTS to 4G: 100 Mb/s downlink and 50 Mb/s uplink, using
OFDM.
38
3GPP: 3rd Generation Partnership Project
Established in Dec. 1998, 3GPP is a collaboration
between
g
rou
p
s of telco associations from across the
g p
w o r l d, s u c h a s E T S I ( E u r o p e ), A R I B/T T C ( J a p a n ),
China, North America, South Korea, etc.
Its aim it to make a globally applicable 3G mobile
phone system specification within the scope of the
ITU’s International Mobile Telecommunications (IMT)-
2000 project.
75
It evolves current GSM systems.
Note: different from 3GPP2, which is another 3G
technology based on IS-95 (CDMA), commonly known
as CDMA2000.
Standard Releases
Version Released
at
Description
Release 98 1998 This and earlier releases s
p
ecif
y

p
re-3G GSM networks
p y p
Release 99 2000 Q1 Specified the first UMTS 3G networks, incorporating a
CDMA air interface
Release 4 2001 Q2 Added features including an all-IP Core Network
Release 5 2002 Q1 Introduced IMS and HSDPA
Release 6 2004 Q4 Integrated operation with Wireless LAN networks
76
Release 7 2007 Q4 Performance improvement
Release 8
Release 9
Mar.2009
Dec. 2009
LTE, All-IP Network (SAE).
SAES Enhancements, Wimax and LTE/UMTS
Interoperability
Release 10 In
progress
LTE Advanced
From wikipedia
39
LTE-advanced Proposals
Various concepts for Relay Nodes
UE Dual TX antenna solutions for SU-MIMO and diversity MIMO
Scalable system bandwidth exceeding 20 MHz Potentially up to
Scalable system bandwidth exceeding 20 MHz
,
Potentially up to
100MHz
Local area optimization of air interface
Nomadic / Local Area network and mobility solutions
Flexible Spectrum Usage
Cognitive Radio
Automatic and autonomous network confi
g
uration and o
p
eration
77
g p
Enhanced precoding and forward error correction
Interference management and suppression
Asymmetric bandwidth assignment for FDD
Hybrid OFDMA and SC-FDMA in uplink
UL/DL inter eNB coordinated MIMO
From wikipedia
LTE vs WiMAX: Air interface
LTE WiMAX
Duplexing method
FDD and TDD
b FDD f
TDD primary profile but
FDD ifi d
Duplexing method
b
ut
FDD f
ocus
FDD
spec
ifi
e
d
too
MIMO mode Diversity/SM/CSM Diversity/SM/CSM
System Bandwidth Scalable: 1.25 ~ 20 MHz Scalable: 3.5 ~ 10 (20) MHz
Modulation 64QAM/16QAM/QPSK 64QAM/16QAM/QPSK
FFT 128 ~ 2048 points 128 ~ 1024 (2048) points
Downlink Access OFDMA OFDMA
Uplink Access
SC
-
FDMA
OFDMA
78
Uplink Access
SC
-
FDMA
OFDMA
Frame Length 0.5ms 5 ms
Source: D. Pulley of Picochip
40
Less obvious at first glance
Mobile WiMAX 20MHz is coming!
LTE has two TDD modes with different frame structures:

pressure is on to reduce on a single one

TDSCDMA successor mode


pressure is on to reduce on a single one TDSCDMA successor mode

this may pre-empt natural selection and resultant could go head to
head with WiMAX TDD profile
SC-FDMA in the Uplink?

WiMAX OFDMA has a peak-mean ratio of approx 10dB

LTE SC-FDMA has lower peak-mean ratio: approx 5dB
∴LTE terminal battery life should be better
High speed packet data rate claims:
79
High speed packet data rate claims:

regardless of air interface, divide the theory or marketing by 3 for
deployable peak base station throughputs for wide area coverage
Source: D. Pulley of Picochip
Over the next 5 years
HSPA builds on existing 2G/3G deployments, licenses and
roaming, and will account for majority of mobile wireless
networks
Mobile WiMAX
can capture
niche market
dependent on
Mobile WiMAX
can capture
niche market
dependent on
spectrum availability, proof of performance (Sprint-Nextel)
Initial coverage limited deployments give HSPA advantage in
CAPEX and OPEX and therefore capital required for launch
and NPV
Lower cost of equipment will not be significant factor
Important to consider other areas such as mobility, latency,
services to be offered revenue streams and overall

eco
80
services to be offered
,
revenue streams
,
and overall eco
-
system”
41
Longer Term Perspective
Improvements in technology performance and resulting link
budget (e.g. 802.16m) can give advantage to WiMAX particularly
for Greenfield operators – but LTE will have advantage of 3GPP
h i
h
er
i
ta
g
e
Later capacity limited scenarios are more favourable to mobile
WiMAX and LTE – mainly in urban areas – but greater
competition from e.g. WiFi hotspots
3GPP and 3GPP2 networks migrate towards OFDMAtechnology
(e.g. LTE, CDMA Rev. C)
This may lead to further market consolidation, depending on
d f LTE/R C d f bil WiMAX
81
spee
d
o
f LTE/R
ev.
C
an
d
success

o
f
current

mo
bil
e
WiMAX
deployments
Who will eventually win? Who knows!
Comparison
WiMAX
Net o k
WiFi
Large
Coverage
Net
w
o
r
k
Simplicity
Broad
Band
82
3G /HSDPA
QoS
Full 
Mobility
Security
42
Wireless Technology Positioning
Mobility / Range
GSM
GPRS
EDGE
W
alk
Vehicle
Pedestrian
High Speed
Vehicular
Rural
Vehicular
Urban
Nomadic
WiMAX with 
limited mobility
Flash‐OFDM 
UMTS
HSDPA
IEEE
83
Data rates
10
Mbps
0.1
IEEE
802.16d
1 100
WLAN
(IEEE 802.11x)
DECT
Bluetooth
EDGE
Fixed
W
Indoor
Personal Area
Fixed urban
Nomadic
IEEE
802.16e
Capacity
Agenda
Wireless LAN (Local Area Networks)
Wireless MAN: WiMAX (IEEE 802.16)
Mobile Cellular Systems
3GPP LTE (Long Term Evolution)
Femto cell and Mobility
84
Q&A
43
Smartphones
Windows Mobile Based: 12% of the market, supports
UMTS, WiFi.
Symbian Based: 65% of the market, Nokia, Sony
Ericsson, support 3G.
RIM OS Based: 11% of the market, Blackberry (not
currently 3G capable to save battery, with the small
exception)
Mac OS
-
like iPhone
-
OS Based: 7% of the market
85
Mac OS
like iPhone
OS Based: 7% of the market
.

Apple's iPhone (using EDGE)
Femto Cell
Also called Access Point Base Station
No dual-mode handset needed, existing handset is fine.
A femto cell is a small cellular base station, typically for indoors,
especiall
y
where access would otherwise be limited or unavailable.
The femtocell incorporates the functionality of a typical base station
but extends it to allow a simpler, self contained deployment
Although much attention is focussed on UMTS, the concept is
applicable to other network technologies, such as GSM, CDMA2000,
TD-SCDMA, WiMAX.
Attractions to mobile o
p
erators: to im
p
rove both covera
g
e and
86
p p
g
capacit
y
, especiall
y
indoors.

There may also be opportunity for new services and reduced cost.
44
Femto Cell Network Arch.
Femto Cell BS
Internet
Macro Cell BS
Macro Network
Broadband Router
87
Mobile Operator
Core Network
Internet
Tunnel 
Example Scenario
Nation Wide
Nation Wide
NetworkNetwork
(Cellular)(Cellular)
Home Home
NetworkNetwork
(WiFi)(WiFi)
Office NetworkOffice Network
(Multiple (Multiple WiFisWiFis))
City WideCity Wide
NetworkNetwork
(WiMAX)(WiMAX)
88
Switch Switch automaticallyautomatically and and seamlessly
seamlessly
from one network to another
from one network to another
45
Contact, Q&A
Dr Kun Yang
School of Comp. Science & Electronic En
g
ineerin
g
(CSEE),
University of Essex, Wivenhoe Park, Colchester,
CO4 3SQ, UK
Email: kunyang@essex.ac.uk
http://privatewww.essex.ac.uk/~kunyang/
89