WiMAX and Mobile WiMAX

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21 Νοε 2013 (πριν από 3 χρόνια και 8 μήνες)

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Wireless Metropolitan Area Networks:

WiMAX and Mobile WiMAX



2

Communication Technology Laboratory

Wireless Communication Group

Outline


Wireless Metropolitan Area Networks



IEEE 802.16 family of WMAN standards


The WiMax Forum


IEEE 802.16 MAC Layer


IEEE 802.16 OFDM based Physical Layer


Mobile WiMAX key features

3

Communication Technology Laboratory

Wireless Communication Group

WBAN

Classification of Wireless Networks


Wireless Wide Area Networks


national coverage


typ. basestation range 10km


typ. user data rate 1Mbps


Wireless Metropolitan Area Networks:
broadband wireless access


city
-
wide coverage


typ. basestation range 1km


typ. user data rate 10Mbps


Wireless Local Area Networks


spot or building coverage


typ. access point range 100m


typ. user data rate 100Mbps


Wireless Personal Area Networks


max. range 10m


typ. user data rates 1Mbps
-

1Gbps (!)


Wireless Body Area Networks


max. range 1m


typ. data rate per node: 100kbps (!)
-

100Mbps


WLAN

WPAN

WMAN

WWAN

802.15

802.11

802.16

802.16e

family of IEEE standards

4

Communication Technology Laboratory

Wireless Communication Group

Broadband Wireless Access


fixed

broadband wireless
access


line of sight (LoS)


non line of sight (NLoS)


mobile

broadband wireless
access


different network
configurations


point
-
to
-
point (P2P)


point
-
to
-
multipoint (PMP)


mesh


subscriber station (SS)


base station (BS)

backhau
l

network

P2P

PMP

SS

mesh

BS

5

Communication Technology Laboratory

Wireless Communication Group

Typical Equipment


BS: base station (indoor
electronics and WiMAX tower)






SS: subscriber station (a user or
group of users sharing a WiMAX
receiver)

Source: [4]

6

Communication Technology Laboratory

Wireless Communication Group

Outline


Wireless Metropolitan Area Networks


IEEE 802.16 family of WMAN standards


The WiMax Forum


IEEE 802.16 MAC Layer


IEEE 802.16 OFDM based Physical Layer


Mobile WiMAX key features

7

Communication Technology Laboratory

Wireless Communication Group

Goals of IEEE 802.16


global standard for wireless
metropolitan area networks
(WMAN)


several km range


throughput comparable to
ADSL


fast installation (including
temporary installations)


scalability for evolutionary
growth (small initial
investment)


wide range of QoS


data rate, latency


constant and variable rate
traffic


connection
oriented



P2P, PMP, mesh


supports a wide range of
carrier frequencies and
bandwidth


operation in licensed and
unlicensed bands
(interference)


efficient handling of
asymmetric traffic


link adaptation


support of multiple antennas

8

Communication Technology Laboratory

Wireless Communication Group

IEEE 802.16 Family


802.16: initial version. 10
-
66 GHz line
-
of
-
sight (LOS) in year 2002


802.16a: extension 2
-
11 GHz (no line
-
of
-
sight) NLOS in year 2003


802.16b: quality of service (QoS)


802.16c: interoperability with protocols and test
-
suite structures


802.16d (802.16
-
2004): improvement of 802.16 and 802.16a (nomadic)


802.16e (802.16e
-
2005): support fixed and mobile broadband (PHY and MAC layers)


802.16f: coverage improvement based on mesh networks


802.16g: support mobility at higher layers


802.16j: mobile multihop relaying


802.16m:
Air Interface for Fixed and Mobile Broadband Wireless Access Systems
-

Advanced Air Interface

Source: [4]

9

Communication Technology Laboratory

Wireless Communication Group

Status of IEEE 802.16 (as of 10/2010)

10

Communication Technology Laboratory

Wireless Communication Group

Status of IEEE 802.16 (as of 10/2010)

http://standards.ieee.org/getieee802/download/802.16
-
2009.pdf


11

Communication Technology Laboratory

Wireless Communication Group

http://www.wimaxforum.org/

http://www.wimaxforum.org/LiteratureRetrieve.aspx?ID=177981

12

Communication Technology Laboratory

Wireless Communication Group

Scope of the Standard


service specific convergence sublayer


convergence functions to support different
protocols (ATM, Ethernet, IP)


handles connection oriented and
connectionless traffic


MAC common part sublayer


medium access


bandwidth management


MAC management signaling


addressing


connection management


security sublayer


privacy


authentification


encryption


four different physical layers


single carrier 11GHz
-
66GHz LoS


single carrier 2GHz
-
11GHz NLoS


OFDM 2GHz
-
11GHz NLoS portable


OFDMA 2GHz
-
6GHz NLoS mobile

CS SAP

MAC SAP

PHY SAP

service specific

convergence sublayer

(CS)

MAC common

part sublayer (CPS)

security


sublayer

physical layer

(PHY)




















data/control

plane

13

Communication Technology Laboratory

Wireless Communication Group

IEEE 802.16 Key Features


Channel bandwidth varying from 1.25 to 20 MHz.


Connection
-
oriented services


Strong security


Multicast support


Low latency,low packet loss handovers


Coverage radius up to 50km theoretical (802.16) or 8km (802.16a)


Data rate up to 75 Mbps


10
-
60 GHz LOS (802.16), 2
-
11GHz NLOS (802.16a)

Source: [4]

14

Communication Technology Laboratory

Wireless Communication Group

Difference and similarity to IEEE 802.11 family (Wi
-
Fi)

WiMAX

Wi
-
Fi

Range

Outdoor long range

Indoor short range

Spectrum

Licensed and unlicensed bands

Unlicensed band

Use

Point
-
to
-
point connection to the
Internet from ISP to end user

Access to network by end
user. Network may or not be
connected to the Internet

Type of access

Fixed (alternative to wired access) to
mobile (like cellphone)

Fixed to pedestrian


If WiMAX provides services analogous to a cellphone, Wi
-
Fi is more analogous to a
cordless phone.



15

Communication Technology Laboratory

Wireless Communication Group

Outline


Wireless Metropolitan Area Networks


IEEE 802.16 family of WMAN standards


The WiMax Forum


IEEE 802.16 MAC Layer


IEEE 802.16 OFDM based Physical Layer


Mobile WiMAX key features

16

Communication Technology Laboratory

Wireless Communication Group

The WiMAX Forum: An Industry
-
Led Non
-
Profit
Organization to Promote IEEE802.16 Systems


IEEE 802.16 offers a huge
array of options


potential source of problems
for compatibility and
interoperability


solution: profiles


the WiMAX forum defines
system and certification
profiles


specific set of parameters for
different application scenarios


and ensures compatibility by
certification



nonprofit organization founded
in June, 2001


more than 400 members as of
2006


mission: facilitate the
deployment of IEEE 802.16
based broadband wireless
equipment by ensuring
compatibility and
interoperability


http://www.wimaxforum.org

17

Communication Technology Laboratory

Wireless Communication Group

WiMAX profiles

System Profiles:


industry selection of features for
MAC and PHY from the 802.16
specifications


determines the required and
conditionally required features for
implementation


maintains the mandatory or optional
status in 802.16 standards


forms the basis for testing
conformance and interoperability


does not exclude other
implementations of the standard

Certification Profiles:


contains band of operation, duplexing
option and bandwidth


an example profile would be 2.5 GHz,
TDD and 5MHz


certification profiles provide a
mechanism to identify devices in
various markets to be certified

Example



the current fixed profiles define for both TDD and FDD profiles



all of the mobile profiles are TDD only



the fixed profiles have channel sizes of 3.5 MHz, 5 MHz, 7 MHz and 10 MHz.



the mobile profiles are 5 MHz, 8.75 MHz and 10 MHz. (Note: the 802.16 standard allows far wider
variety of channels, but only the above subsets are supported as WiMAX profiles).

18

Communication Technology Laboratory

Wireless Communication Group

Spectrum allocation


There is no uniform global licensed spectrum for WiMAX.


In the US, the biggest segment available is around 2.5 GHz,


Elsewhere in the world, the most likely bands used will be around 3.5
GHz, 2.3/2.5 GHz, or 5 GHz,


2.3/2.5 GHz probably being most important in Asia.


Analogue TV bands may become available for WiMAX use,


await the complete rollout of digital TV.


In the U.S. The FCC auction for this spectrum is scheduled for the end
of 2007.


EU has suggested re
-
allocation of 500
-
800 MHz spectrum for wireless
communication, including WiMAX.


Manufacturers are compelled to provide multi
-
spectrum devices that
can be used across different regions and regulatory requirements.

19

Communication Technology Laboratory

Wireless Communication Group

World frequency map


WCS: Wireless Communication Systems

BRS: Broadband Radio Service

20

Communication Technology Laboratory

Wireless Communication Group

Spectral Auction of the 700MHz TV Band in the USA
(Spring 2008)

21

Communication Technology Laboratory

Wireless Communication Group

Results of the Spectral Auction in Germany, Spring
2010 („Digitale Dividende“)

22

Communication Technology Laboratory

Wireless Communication Group

IEEE 802.16 Mobility Support and WiMAX
Forum Usage Scenarios

handover

23

Communication Technology Laboratory

Wireless Communication Group

Outline


Wireless Metropolitan Area Networks


IEEE 802.16 family of WMAN standards


The WiMax Forum


IEEE 802.16 MAC Layer


IEEE 802.16 OFDM based Physical Layer


Mobile WiMAX key features

24

Communication Technology Laboratory

Wireless Communication Group

IEEE 802.16 MAC


MAC supports multiple 802.16 PHY layers


In IEEE802.11 the most widely used MAC is contention based
(DCF)


robust, as it does not require central coordination


difficult to meet QoS requirements


connection
-
less MAC service


In contrast, the 802.16 MAC uses a scheduling algorithm. The SS
need to compete once (for initial entry into the network).


after that it is allocated an access slot by the base station.


the time slot can enlarge and contract, but remains assigned to the
subscriber station which means that other subscribers cannot use it.


connection
-
oriented MAC service.


the scheduling algorithm also allows the base station to control QoS
parameters by balancing the resource assignments among the SSs.

25

Communication Technology Laboratory

Wireless Communication Group

MAC Key Features

Source: [4]

26

Communication Technology Laboratory

Wireless Communication Group

Outline


Wireless Metropolitan Area Networks


IEEE 802.16 family of WMAN standards


The WiMax Forum


IEEE 802.16 MAC Layer


IEEE 802.16 OFDM based Physical Layer


Mobile WiMAX key features

27

Communication Technology Laboratory

Wireless Communication Group

WiMAX PHY


single carrier 11GHz
-
66GHz LoS


single carrier 2GHz
-
11GHz NLoS


OFDM 2GHz
-
11GHz NLoS
portable: WMAN
-
OFDM



OFDMA 2GHz
-
6GHz
NLoS mobile:
WMAN
-
OFDMA

28

Communication Technology Laboratory

Wireless Communication Group

WirelessMAN
-
OFDM and
-
OFDMA Overview


CC: convolutional code


RS: Reed Solomon Code


CTC: convolutional turbo code


BTC: block turbo code


LDPC: low density parity check code


AAS: adaptive antenna systems


STC: space
-
time coding


MIMO: multiple input multiple output (spatial
multiplexing)

source: [1]

29

Communication Technology Laboratory

Wireless Communication Group

OFDM PHY Key Features

Source: [4]

30

Communication Technology Laboratory

Wireless Communication Group

OFDM subcarrier assignment


256 subcarriers


192 data subcarriers


56 NULL subcarriers


8 pilot subcarriers


system bandwidth W is an integer multiple of
1.25MHz, 1.5MHz, 1.75MHz, 2MHz or 2.75MHz


proportional to the temporal sampling frequency F
s


to achieve different system bandwidths, the equipment
must support different sampling frequencies


the duration of the OFDM symbol is approximately
given by






the variable
g

determines the guard time (cyclic
extention) between consecutive OFDM symbols


-
128

-
101

0

-
88

-
63

-
38

-
13

....

....

....

.

128

101

0

88

63

38

13

....

....

....

.

subcarrier index

frequency

NULL subcarrier

data subcarrier

pilot subcarrier

subcarrier spacing F

system bandwidth W



256
1.15
8 16 32 64
G
g
T
W
g




....

....

31

Communication Technology Laboratory

Wireless Communication Group

OFDM subchannels


TDM multiplexing on DL


full OFDM symbol allocated to a SS


on UL optional subchannels


each SS uses only a nonoverlapping
fraction of all subcarriers of an OFDM
symbol


each subchannel has 12 data
subcarriers and 1 pilot subcarrier


four chunks of 3 data subcarriers each


maximum 16 subchannels


SS may use 1, 2, 4, 8 or 16
subchannels


the data subcarrier chunks of each
subchannel are distributed across the
whole system bandwidth


impact on channel estimation (channel
estimation on basis of preamble)

31

17

15

1

29

.

.

.


.

.

.


SS A

SS B

SS A

SS C

time

subchannel index

3

32

Communication Technology Laboratory

Wireless Communication Group

OFDM: modulation and coding schemes

Rate ID

modulation
rate

Coding

information
bit/symbol

information
bit/OFDM
symbol

Peak data
rate in 5
MHz
(Mbps)

0

BPSK

1/2

0.5

88

1.89

1

QPSK

1/2

1

184

3.95

2

QPSK

3/4

1.5

280

6.00

3

16QAM

1/2

2

376

8.06

4

16QAM


3/4

3

568

12.18

5

64QAM


2/3

4

760

16.30

6

64QAM

3/4

4.5

856

18.36

33

Communication Technology Laboratory

Wireless Communication Group

Outline


Wireless Metropolitan Area Networks


IEEE 802.16 family of WMAN standards


The WiMax Forum


IEEE 802.16 MAC Layer


IEEE 802.16 OFDM based Physical Layer


Mobile WiMAX key features

34

Communication Technology Laboratory

Wireless Communication Group

Mobile WiMAX


in December 2005 the IEEE ratified the
802.16e amendment


support mobility


WiMAX forum is defining system
performance and certification profiles


air interface


network architecture necessary to
implement an end
-
to
-
end Mobile
WiMAX network


Mobile Technical Group (MWG)


air interface (mandatory and optional
features of the IEEE standard)


release
-
1 covers 5, 7, 8.75 and 10MHz
channel bandwidth at 2.3, 2.5 3.3 and
3.5GHz bands


Network Working Group (NWG)


higher layer networking specifications


35

Communication Technology Laboratory

Wireless Communication Group

WiMAX Design

Challenges


Mobility causes the SS to communicate with several BS


Identification must be fast and reliable. More demanding
than for fixed systems.


Full mobility: the user expects a seamless connection
(similar to 3G/4G systems)


Mobility support for the transport (IP) layer: may require
authentication and handoffs for up and downlink IP packets and
MAC frames


Support low power devices (battery autonomy)

36

Communication Technology Laboratory

Wireless Communication Group

Overview of
Key Features


Scalable OFDMA
: scaling of channel bandwidth by FFT size with constant subcarrier
spacing


results in a higher spectrum efficiency in wide channels


cost reduction in narrow channels


Improving NLOS coverage by


advanced antenna diversity schemes


hybrid
-
Automatic Retransmission Request (hARQ) error control


Improving capacity and coverage by


Adaptive Antenna Systems (AAS)


Multiple Input Multiple Output (MIMO) wireless


Increasing system margin by use of denser sub
-
channelization


improves indoor penetration


High
-
performance coding techniques such as Turbo Coding and Low
-
Density Parity
Check coding (LDPC) enhance outage probability and NLOS performance


Downlink and uplink sub
-
channelization

(multiple users per OFDM symbol)
improves coverage, spectral efficiency and sum rate


New QoS class (enhanced real
-
time Polling Service) is more appropriate for VoIP
applications.


Support for mobility

(soft and hard handover (latencies < 50ms) between base
stations)


most important aspects of WirelessMAN
-
OFDMA

37

Communication Technology Laboratory

Wireless Communication Group

Time Division Duplex (TDD)


Standard supports TDD and FDD


But only TDD in the WiMAX mobile profile.


TDD enables adjustment of the downlink/uplink ratio to efficiently
support asymmetric downlink/uplink traffic, while with FDD, downlink
and uplink always have fixed and generally, equal DL and UL
bandwidths.


TDD assures channel reciprocity for better support of link adaptation,
MIMO and other closed loop advanced antenna technologies.


Unlike FDD, which requires a pair of channels, TDD only requires a
single channel for both downlink and uplink providing greater flexibility
for adaptation to varied global spectrum allocations.


Transceiver designs for TDD implementations are less complex and
therefore less expensive.

38

Communication Technology Laboratory

Wireless Communication Group

FUSC and PUSC subchannels


support of subchannels on DL/UL


minimum frequency
-
time resource
unit is one slot (48 data
subcarriers)


two types of subcarrier
permutations


diversity: random subcarrier
selection across whole frequency
band.


Provides diversity and inter
-
cell
interference averaging


contiguous: block of adjacent
subcarriers. Used for adaptive
modulation and coding (AMC) and
multiuser diversity.


DL fully used subcarriers (DL
-
FUSC)


each subchannel contains only
data subcarriers


a common set of pilot tones is
used by all subchannels


used, if all data subcarriers are
allocated to subchannels (this
may not be possible due to inter
-
cell interference)


requires the smallest overhead


DL partially used subcarriers (DL
-
PUSC)


six groups of subcarriers


each group uses individual pool of
pilot subcarriers


the subchannels contain only data
tones


UL
-
PUSC


each subchannel has its own pilot
tones (required, because each
subchannel may originate from a
different user



39

Communication Technology Laboratory

Wireless Communication Group

SOFDMA Subcarrier Allocation and Modulation
Schemes

CC: convolutional code

CTC: convolutional turbo code


Optional:



Italic entries



Block turbo code and Low Density Parity
Check code (LDPC)

symbol period not affected

by system bandwidth

uplink requires more pilots

due to OFDMA (each user

has different channel)

40

Communication Technology Laboratory

Wireless Communication Group

SOFDMA Parameters

Source: [1]

41

Communication Technology Laboratory

Wireless Communication Group

Fractional Frequency Reuse


Users close to the BS operate on the zone with all subchannels available
(F1+F2+F3)


For the edge users, each cell or sector operates on the zone with a faction
of the subchannels available (F1, F2 or F3)


Frequency reuse 1 for center users for max spectral efficiency


Fractional frequency reuse for edge users to assure connection quality and
throughput

Source: [1]

42

Communication Technology Laboratory

Wireless Communication Group

Advanced Antenna Systems


Smart antennas increase the spectral density and the
SNR. Supported are:


Spatial diversity (> 1 antenna at BS, placed at least half a
wavelength apart, for selection combining)


Spatial multiplexing (SM) and collaborative SM


For the UL, each user has a single transmit antenna, and two users
can transmit collaboratively in the same timeslot


Beamforming antennas


Space
-
time codes (TX diversity like Alamouti scheme)

Source: [1],[4]

43

Communication Technology Laboratory

Wireless Communication Group

Maximum Data Rates for SIMO/MIMO
Configurations (Mandatory Regime)


bandwidth 10MHz


frame duration 5ms


uplink: max. 16
-
QAM; r=3/4 CTC


downlink: max. 64
-
QAM; r=5/6
CTC


PUSC sub
-
channels


44 data OFDM symbols

one sector

comprises
multiple
users

collaborative

MIMO"

44

Communication Technology Laboratory

Wireless Communication Group

QoS Categories

Source: [1]

45

Communication Technology Laboratory

Wireless Communication Group

MAC scheduling services


the scheduler efficiently allocates
resources in response to bursty data
traffic and changing channel conditions


the scheduler at the basestation
schedules both DL and UL traffic


requires accurate and timely
information about MS traffic conditions
and QoS requirements


multiple UL bandwidth request
mechanisms


ranging channel


piggyback requests (with data payload)


polling (by basestation)


the UL service flow defines the
feedback mechanism for each UL
connection




dynamic resource allocation


support of time, space and frequency
resource allocation on a per
-
frame
basis


delivered in the MAP messages at the
beginning of each frame


benefit of doing the UL scheduling at
the BS


BS knows the QoS requirements of all
MS and can allocate the UL resources
more efficiently


46

Communication Technology Laboratory

Wireless Communication Group

Sources

[1]
Mobile WiMAX


Part 1: A Technical Overview and Performance
Evaluation
. WiMAX Forum. August 2006.

http://www.wimaxforum.org/technology/downloads/Mobile_WiMAX_Part1_Overview_and_Performance.pdf

[2]
WiMAX
.

Intel Technology Journal. Vol 8, issue 3. August 2004.

ftp://download.intel.com/technology/itj/2004/volume08issue03/vol8_iss03.pdf

[3]
Introduction to WiMAX Air Interface.
S. Shawn Tsai.

Business Unit Access, Ericsson AB. September 2006. Presentation NCTU

http://140.113.13.93/wireless/download/material/NCTU%20Tutorial%20one%20per%20page.pdf

[4]
WiMAX: taking wireless to the MAX
. Deepak Pareek
-

Auerbach
Publications c/o Taylor & Francis. 2006.

http://www.itknowledgebase.net/books/4565/au7186_fm.pdf

(e
-
text from ETH
-
Bibliothek)

[5]
WiMax and Wi
-
Fi: Separate and Unequal,
Cherry, S.M.

Spectrum, IEEE, Vol.41, Iss.3, March 2004.

http://ieeexplore.ieee.org/iel5/6/28451/01270541.pdf?isnumber=28451∏=JNL&arnumber=1270541&arnumber
=1270541&arSt=+16&ared=+16&arAuthor=Cherry%2C+S.M.




Mobile Radio Standards (10/2011)

47

Communication Technology Laboratory

Wireless Communication Group

http://en.wikipedia.org/wiki/Template:Cellular_network_standards

Commercial Deployment Example: Clearwire

48

Communication Technology Laboratory

Wireless Communication Group

http://www.clearwire.com/

http://www.clear.com/discover