4G M OBILE W IRELESS W I MAX W SS W MAX Aditya K. Jagannatham - - PowerPoint PPT Presentation

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4G M O 4G M OBILE W IRELESS W I MAX W SS W MAX Aditya K. Jagannatham Indian Institute of Technology Kanpur Indian Institute of Technology Kanpur Commonwealth of Learning Vancouver MOOC on M4D 2013 WSSUS Channel Variables Delay WSSUS Channel

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SLIDE 1

4G MO W

SS W MAX

4G MOBILE WIRELESS WIMAX

Aditya K. Jagannatham Indian Institute of Technology Kanpur Indian Institute of Technology Kanpur Commonwealth of Learning Vancouver

MOOC on M4D 2013

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SLIDE 2

WSSUS Channel Variables Delay WSSUS Channel Variables ‐ Delay

  • Typical wireless channel delay spreads are of the
  • rder of 3 μs.

~ Km ~ Km ~ Km

MOOC on M4D 2013

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SLIDE 3

WSSUS Channel Variables Delay WSSUS Channel Variables ‐ Delay

  • Therefore, to avoid ISI, T > Td = 3 μs.
  • It is immediately clear the maximum symbol rate in
  • utdoor channels is,

1 Kbps 333 10 3 1

6 max

  

R

MOOC on M4D 2013 3

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SLIDE 4

Coherence bandwidth Coherence bandwidth

  • Coherence bandwidth of the channel is defined in

terms of delay spread as,

c

T B 1 

d c

T

  • For outdoor channels, Td ~ 3 s as seen earlier.

– Hence, the coherence bandwidth Bc is given as, ,

c

g ,

KHz 333 1   B

MOOC on M4D 2013

KHz 333 10 3

6 

 

 c

B

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SLIDE 5

Single Carrier Schematic Single Carrier Schematic

B B/2 B/2 B/2

Carrier

‐B/2

MOOC on M4D 2013 5

B = 10 – 20 MHz

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SLIDE 6

Single Carrier Vs Multi Carrier Single Carrier Vs. Multi Carrier

  • Consider instead a multi‐carrier modulation

(MCM) with N sub‐bands of bandwidth B/N. ( ) E h b d f b d id h B/N h b i

  • Each band of bandwidth B/N has a subcarrier.

MOOC on M4D 2013 6

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SLIDE 7

Multi Carrier Schematic Multi Carrier Schematic

B

B/N 2B/N B/2 ‐B/N ‐2B/N ‐(N/2‐1)B/N

B/N

Subcarriers

MOOC on M4D 2013 7

B = 10 MHz, N = 1000, B/N = 10 KHz

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SLIDE 8

Multi Carrier Communication Multi‐Carrier Communication

  • The N subcarriers are at frequencies

N B N N B N B N B N N B N                        2 , , , , , , 2 2 , 1 2  

  • The ith SC is at if

where f = B/N is the

     

The i SC is at ifo, where fo = B/N is the fundamental frequency of the multi‐carrier t system.

                  2 1 2 , N i N N B i if f

  • i

MOOC on M4D 2013 8

        2 2 , N f f

  • i
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SLIDE 9

MCM – Overall Rate MCM – Overall Rate

  • In an MCM system one is transmitting N

In an MCM system, one is transmitting N parallel symbols over time N/B.

bols rriers lel sym subcar N paral Over N N O

MOOC on M4D 2013 9

Symbol Time = N/B

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SLIDE 10

Orthogonal Frequency Division Multiplexing (OFDM)

  • By converting a wideband channel into

By converting a wideband channel into multiple orthogonal narrowband channels,

  • ne can tremendously simplify the receive
  • ne can tremendously simplify the receive

processing.

If the subcarrier bandwidth is less than the – If the subcarrier bandwidth is less than the coherent bandwidth, then each narrowband carrier experiences flat‐fading. carrier experiences flat fading.

  • It can be processed with much lower

complexity compared to frequency selective complexity compared to frequency‐selective fading.

MOOC on M4D 2013 10

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SLIDE 11

Orthogonal Frequency Division Multiplexing

  • Orthogonal subcarriers

Orthogonal Subcarriers in OFDM for WiMAX

  • Orthogonal subcarriers

in a WiMAX system

0.8 g

with a carrier spacing

  • f 15.625 KHz.

0.4 0.6 er Amplitude

  • Observer, there is NO

guard band

0.2 Subcarrie

guard band

– Hence, efficient use of

  • 60
  • 40
  • 20

20 40 60

  • 0.2

Frequency (KHz)

spectrum

q y ( )

MOOC on M4D 2013 11

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SLIDE 12

Orthogonal Frequency Division Multiplexing Multiplexing

  • An OFDM schematic employing a bank of

modulators (BoM) is given below.

S/P Demux Bank Of Modulators Summer

nnel

k

Cha

Bank

  • f

Correlators P/S Mux Repeater

MOOC on M4D 2013 12

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SLIDE 13

WIMAX W I WORLDWIDE INTEROPERABILITY FOR

MICROWAVE ACCESS

MOOC on M4D 2013

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SLIDE 14

WiMAX Timeline Beginnings WiMAX Timeline ‐ Beginnings

  • IEEE 802 16 group was formed in 1998

IEEE 802.16 group was formed in 1998

– To develop an air‐interface standard for wireless b db d broadband.

  • Initially focused at development of an LOS‐

based point‐to‐multipoint WBS.

– Slated for operation in the 10GHz–66GHz Slated for operation in the 10GHz 66GHz millimeter wave band.

MOOC on M4D 2013 14

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SLIDE 15

WiMAX Timeline Beginnings WiMAX Timeline ‐ Beginnings

  • The resulting standard—the original 802.16

was completed in December 2001. p

  • Salient features of this standard included

Si l i h i l (PHY) l – Single‐carrier physical (PHY) layer. – Burst time division multiplexed (TDM) MAC layer.

MOOC on M4D 2013

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SLIDE 16

WiMAX Timeline Precursor WiMAX Timeline ‐ Precursor

  • The IEEE 802.16 group subsequently produced

802.16a, an amendment to the 802.16 standard.

– Included NLOS applications in the 2GHz–11GHz band (Multipath Propagation). – Employed an Orthogonal Frequency Division Multiplexing (OFDM) based physical layer. – Additions to the MAC (Medium Access Control) layer, such as support for Orthogonal Frequency Division Multiple Access (OFDMA), were also included.

MOOC on M4D 2013 16

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SLIDE 17

WiMAX Timeline Precursor WiMAX Timeline ‐ Precursor

  • Further revisions resulted in a new standard

in 2004, called IEEE 802.16‐2004.

– This formed the basis for the first WiMAX solution. solution.

MOOC on M4D 2013

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SLIDE 18

WiMAX Timeline Inception WiMAX Timeline ‐ Inception

  • Early solutions based on the IEEE 802.16‐

y 2004 targeted fixed applications.

– Referred to as fixed WiMAX. Referred to as fixed WiMAX.

  • In December 2005, the IEEE 802.16 group

completed and approved IEEE 802 16e completed and approved IEEE 802.16e‐ 2005.

A d d th li fi d WiMAX IEEE 802 16 – Amended the earlier fixed WiMAX IEEE 802.16‐ 2004 standard to add mobility support. Thi f th b i f th WiMAX l ti f – This forms the basis for the WiMAX solution for mobile applications. Oft f d t bil WiMAX

MOOC on M4D 2013

– Often referred to as mobile WiMAX.

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SLIDE 19

PHY (Physical) Layer PHY (Physical) Layer

  • PHY is responsible for transmission and

PHY is responsible for transmission and reception of radio signals

  • The WiMAX physical layer (PHY) is based on

Orthogonal Frequency Division Multiplexing. g q y p g

– This offers simplified reception in multipath and allows WiMAX to operate in NLOS conditions. allows WiMAX to operate in NLOS conditions. – OFDM is now widely recognized as the PHY of choice for mitigating multipath in Broadband choice for mitigating multipath in Broadband Wireless Access (BWA) – WLAN, LTE, Bluetooth

MOOC on M4D 2013 19

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SLIDE 20

WiMAX OFDM Parameters

Parameter Fixed Mobile WiMAX Parameter Fixed WiMAX Mobile WiMAX Number of Subcarriers 256 128 512 1024

2048

Used data subcarriers 192 72 360 720

1440

Pilot subcarriers 8 12 60 120

240

/

368

Number of null/guardband subcarriers 56 44 92 184

368

Cyclic Prefix 1/32, 1/16, 1/8, 1/4 Oversampling Rate (Fs/BW) Depends on BW. 7/6 for 256 OFDM, 8/7 for multiples of 1.75 MHz and 28/25 for multiples of 1.25 MHz, 1.5 MHz, 2 MHz or 2 75 MHz MHz or 2.75 MHz. Channel BW (MHz) 3.5 1.25 5 10

20

Subcarrier spacing 15.625 10.94 p g MOOC on M4D 2013

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SLIDE 21

WiMAX Features WiMAX Features

  • WiMAX Supports Several Advanced Features
  • WiMAX Supports Several Advanced Features

– Scalable Data rate and number of subcarriers (128 – 2048) – Adaptive Modulation and Coding (Number of bits per symbol and Error Control) – High Peak Data Rates ~ 75‐100 Mbps g p – Advanced Antenna Techniques

MOOC on M4D 2013

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SLIDE 22

WiMAX Features WiMAX Features

Alamouti Space‐Time Code Space‐Time Code

Beamforming Beamforming Directional Transmission Spatial Multiplexing Transmission of Multiple Streams

MOOC on M4D 2013

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SLIDE 23

WiMAX Features WiMAX Features

  • Support for TDD and FDD

Support for TDD and FDD

– Fixed‐WiMAX and mobile‐WiMAX support both TDD d FDD TDD and FDD. – This allows for a low‐cost system implementation.

MOOC on M4D 2013 23

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SLIDE 24

Flexible & Dynamic Resource Alloc Flexible & Dynamic Resource Alloc.

  • Both UL and DL resource allocation are controlled

by a scheduler in the BS.

  • Capacity is shared among multiple users on a

p y g p demand basis, using a burst TDM scheme.

  • Further, using the OFDMA‐PHY mode,

multiplexing is additionally done in the frequency dimension.

B ll i diff b f OFDM b i – By allocating different subsets of OFDM subcarriers to different users.

  • Resources may be allocated in the spatial domain
  • Resources may be allocated in the spatial domain

employing Advanced Antenna Systems (AAS).

MOOC on M4D 2013 24

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SLIDE 25

OFDMA Resource Allocation

Frequency Time

MOOC on M4D 2013 25

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SLIDE 26

WiMAX Frame Structure WiMAX Frame Structure

Guard Time FCH MAP DL B #2 Burst 1 F AP UL‐M DL Burst #2 Burst 3 Burst 2 Preamble DL‐MA DL Burst #1 DL Burst #4 DL Burst #3 DL B t CK‐CH Burst 4 Burst 3 P MAP DL Burst #5 DL Burst #6 AC Burst 5 UL‐ DL Burst 7

Ranging

Fast Feedback MOOC on M4D 2013 DL Subframe UL Subframe 26

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SLIDE 27

WiMAX Scheduling Services WiMAX Scheduling Services

  • MAC uses a scheduling service to deliver and

handle services with different QoS reqs. q

  • Determines the mechanism the network uses

to allocate UL and DL resources for the to allocate UL and DL resources for the services.

MOOC on M4D 2013 27

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SLIDE 28

WiMAX Scheduling Services

Scheduler type Services Unsolicited grant services Support for fixed‐size data packets at a constant bit Unsolicited grant services (UGS): Support for fixed size data packets at a constant bit rate (CBR). ‐ Voice Real‐time polling services Designed to support real‐time service flows, such as p g (rtPS): g pp , MPEG video, that generate variable‐size data packets

  • n a periodic basis. ‐ Video

Non‐real‐time polling service (nrtPS): Designed to support delay‐tolerant data streams, such as an FTP, that require variable‐size data grants at a minimum guaranteed rate. g Best‐effort (BE) service: Supports data streams, such as Web browsing, that do not require a minimum service‐level guarantee. – q g Internet, e‐mail Extended real‐time variable t (ERT VR) i For real‐time applications, such as VoIP with silence i th t h i bl d t t b t i

MOOC on M4D 2013

rate (ERT‐VR) service suppression, that have variable data rates but require guaranteed data rate and delay.

28

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SLIDE 29

Mobility Support y pp

  • WiMAX supports the following types of

mobilit mobility

Type Features Nomadic. The user is allowed to take a fixed subscriber station and reconnect from a different point of attachment. Portable. Nomadic access is provided to a portable device, such as a PC card with expectation of a best‐effort handover as a PC card, with expectation of a best effort handover. Simple mobility. The subscriber may move at speeds up to 60 kmph with brief interruptions (less than 1 sec) during handoff. Full mobility: Up to 120 kmph mobility and seamless handoff (less

MOOC on M4D 2013

Full mobility: Up to 120 kmph mobility and seamless handoff (less than 50 ms latency and <1% packet loss) is supported.

29

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SLIDE 30

30

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SLIDE 31

AAA Authentication, Authorization, Accounting

Reference Network Architecture

ASN‐GW Access Service Network Gateway ASP Application Service Provider MIP HA Mobile IP Home Agent MIP‐HA Mobile IP Home Agent MS Mobile Station OSS Operational Support Systems BSS Business Support Systems BS AAA

Internet

ASP MS BS

IP

MIP‐HA

IP Network

MS BS

Access Network

ASN GW

IP Network

OSS/

PSTN

MS BS BSS Gateway

MOOC on M4D 2013

3GPP/ 3GPP2

ASN CSN

31