WiMax Applied Radio Network Planning

WiMax WiMax Applied Radio Network PlanningApplied Radio Network Planning

Course ObjectivesCourse Objectives

At the end of this course you’ll be able to:

• Understand the concept of WIMAX

• Understand the basics of standards related to WIMAX

• Study propagation conditions in WIMAX applications

• Understand some cell planning conditions

• Estimate traffic capacity

• Planning considerations

• Use some Optimization recommendations

• Review new standard for WIMAX Mobile

Course StructureCourse Structure

Day 1 (AM)

• Introduction and Overview

• WiMax Forum

• Physical and MAC Layers

Day 1 (PM)

• Propagation Environments

• Cell Planning

Course StructureCourse Structure

Day 2 (AM)

• Link Budget

• Capacity Planning

• Optimization Process

Day 2 (PM)

• WiMax Mobile

• Course Evaluation and

Feedback

1- Introduction and Overview1- Introduction and Overview

Section 1 – Introduction and Overview


IEEE 802.16 HistoryIEEE 802.16 History


IEEE 802.16 EvolutionIEEE 802.16 Evolution


IEEE 802.16 SpectrumIEEE 802.16 Spectrum

ISM

UNII

INT’L

MMDS

ISM

WCS

UPCS

ISM

UHF

0 1 2 3 4 5 6 7 8 9 10 11

Licensed

Licensed-exempt

GHz

License & License-exempt Spectrum

IEEE 802.16 Spectrum (2)IEEE 802.16 Spectrum (2)UHF 0.75 - 0.8 Channels 60-69, called the upper 700 MHz, are by congressional statute to be

reclaimed for new services (broadband wireless).

ISM 0.9 - 0.93 Industrial, Scientific & Medical Band – License exempt band

UPCS 1.91 - 1.93 License exempt Personal Communications Services

WCS 2.3 Wireless Communications Service. Licensed by Verizon, Bellsouth & AT&T

ISM 2.4 - 2.48 Industrial, Scientific & Medical Band – License exempt band

MMDS 2.5 - 2.7 Multi-channel Multipoint Distribution Service. Licensed in U.S. by Sprint, Worldcom & Nucentrix.

Int’l 3.4 - 3.6 Licensed Bands- Europe, Latin America, Asia (China)

Lower & Mid U-NII

5.15 - 5.355.47 – 5.72

License exempt National Information Infrastructure band. 255 MHz of spectrum recently added per WRC recommendation between 5.47 and 5.72 GHz.

Upper U-NII +

ISM

5.73-5.85 Industrial, Scientific & Medical Band – License exempt band. In many countries this band targeted for outdoor applications and allows for higher EIRP (4W vs 1W)


Wimax in movementWimax in movementSection 1 – Introduction and Overview

Total Subscribers Worldwide (2005-2009)

50.4

118.9

228.9

366.9

32.1

67.9

122.2

187.8

251.9

5

7

10

17.2

24.6

536

0 200 400 600

2005

2006

2007

2008

2009Fixed & MobileWimax

CDMA2000 1xEV

WCDMA/HSDPA

Subscriber in Millions

2- WiMax Forum2- WiMax Forum

Section 2 – WiMax Forum


What is WiMax Forum?What is WiMax Forum?


1.-Applications of Broadband Wireless1.-Applications of Broadband Wireless


2.-Certification2.-Certification

Certification = Conformance + Interoperability

WiMax Forum timeline certificationWiMax Forum timeline certificationSection 2 – WiMax Forum

2005 2006 2007802.16-2004 lab

opens *Air protocol

certification Outdoor *Service certification

Outdoor *Indoor certification *802.16e lab opens *

802.16e first certification *

WiMax Forum certification profileWiMax Forum certification profileSection 2 – WiMax Forum

Frequency (MHz)

Duplexing Channels(MHz) IEEE Standard

3400-3600 TDD 3.5 802.16-2004

3400-3600 FDD 3.5 802.16-2004

3400-3600 TDD 7 802.16-2004

3400-3600 FDD 7 802.16-2004

5725-5850 TDD 10 802.16-2004

Types of access to a Wimax NetworkTypes of access to a Wimax NetworkSection 2 – WiMax Forum

Definition Devices Locations/

Speed

HandOffs 802.16-2004

802.16e

Fixed access

Outdoor & Indoor CPEs

Single/

Stationary

No Yes Yes

Nomadic access

Indoor CPEs PCMCIA cards

Multiple/

Stationary

No Yes Yes

Portability Laptop PCMCIA or mini cards

Multiple/

Walking speed

Hard handoffs No Yes

Simple mobility

Laptop PCMCIA or minicards or smartphones

Multiple/ Low

Vehicular speed

Hard handoffs No Yes

Full mobility Laptop PCMCIA or minicards, PDAs or smartphones

Multiple/High

Vehicular speed

Soft handoffs No Yes

3- Physical and MAC Layers3- Physical and MAC Layers802.16-2004802.16-2004

Section 3 – Physical and MAC Layers


Physical LayerPhysical Layer

• OFDM (Orthogonal Frequency Division Multiplexing)

OFDM OFDM

•PSD (Power Spectral Density)

•All carriers are transmitted in parallel with same amplitude

•OFDM with 256 sub channels

•OFDM uses overlapping sub-channels and the signals can still be received without adjacent interference



Physical LayerPhysical Layer• Sub channelization (Optional)

•Full BW User 1 •Sub-channelized User 2 •Sub-channelized User 3

•2 sub-channels (figurative)

•Frequency

•Po

we

r

•Sub Channelization in the uplink is an option within WiMAX.

•Without subchannelization, cause the link budget to be asymmetrical, this causes the system range to be up link limited

Sub channelizationSub channelization

•Sub channeling concentrates the transmit power into fewer OFDM carriers; this is what increases the system gain that can either be used to extend the reach of the system, overcome the building penetration losses, and or reduce the power consumption of the CPE.

•Not totally deployed for OFDM but is totally functional for OFDMA



Physical LayerPhysical Layer• Directional antennas and diversity reception (Optional)

•Uplink improvement

•Directional antennas increase the fade margin by adding more gain

•This increases the link availability


• AAS (Adaptive Antennas System)


•Are an optional part of the 802.16 standard.

•These have beam forming properties that can steer their focus to a particular direction or directions.

•This means that while transmitting, the signal can be limited to the required direction of the receiver; like a spotlight.

•They also have the property of suppressing cochannel interference from other locations.


Physical Layer Physical Layer • Adaptive Modulation


• Power Control (PC)

•Power control algorithms are used to improve the overall performance of the system, it is implemented by the base station sending power control information to each of the CPEs to regulate the transmit power level so that the level received at the base station is at a pre-determined level

•In a dynamical changing fading environment this pre-determined performance level means that the CPE only transmits enough power to meet this requirement

•Are an optional part of the 802.16 standard.

•For LOS the transmit power of the CPE is approximately proportional to it’s distance from the base station, for NLOS it is also heavily dependant on the clearance and obstructions.


MAC LayerMAC Layer

• Protocol point-multi-point

• Terminal could be shared among many end-user equipment (phones and pc’s)

• QoS defined for each service

• GoS and traffic parameters

• Downlink is multiplex with TDM

• Uplink is shared with TDMA

• 802.16 is connection oriented

MAC LayerMAC Layer

• Upon entering the network, three management connections are established, in both directions. Every connection is used for different QoS connection type:

1. Basic connection – used to transfer of short, time critical MAC and RLC messages

2. Secondary management Connection – used for transfer of standard-based protocols such as DHCP,TFTP,SNMP

3. - Other types of connection, like connection reserved for broadcasting


4- Propagation Environments4- Propagation Environments

Section 4 – Propagation Environments


NLOS & LOS (1)NLOS & LOS (1)

CPE location

WiMax base station location

Fresnel zone clearence

0.6


NLOS

LOS


TIREMTIREM• TIREM (Terrain Integrated Rough Earth Model)

TIREM system uses terrain profiles to compute point-to-point transmission loss at frequencies between 20 MHZ and 20 GHz


Modified Stanford University Interim: SUI channelsModified Stanford University Interim: SUI channels

• Defines three terrain types:

• A: The maximum path loss category is hilly terrain with moderate-to-heavy tree densities

• B: Intermediate path loss condition

• C:The minimum path loss category is mostly flat terrain with light tree densities

• For a given close-in distance d0, the median path loss (PL in dB) is given by

• Defined for AT&T Wireless in US for 1.9 GHz in 1995 Macrocell

sddAPL )/(log10 010



• where A = 20 log10(4 π d0 / λ)

• (λ being the wavelength in m), γ=is the path-loss exponent with γ=(a – b hb + c / hb)

• For hb between 10 m and 80 m (hb is the height of the base station in m), d0 = 100m and a, b, c are constants dependent on the terrain category



•Fade Distribution, K-Factor



•Although the SUI model proposes different sets of parameters for three types of environments, the categories are not specified in a particularly systematic manner and do not explicitly include urban and suburban environments.

5- Cell Planning5- Cell Planning

Section 5 – Cell Planning


Basic considerationsBasic considerations


Quasi PlanningQuasi Planning•Case 1: Medium City

•Population: 2 millions

•Estimated users: 100,000

•Surface to cover: 20 Km2

•Types of services: Wide Band

•Terrain type: mostly flat with some hills at downtown

•Number of sites for first stage: 4

•Number of sectors: 3

•Antenna gain: 19 dBi

•Transmission power: 2 W

•Antenna vertical aperture: 7 degrees

•Antenna horizontal aperture: 120 degrees

•Antennas azimuth: 0, 120 and 240 or 60, 180 and 300

•Antennas downtilt: -4 degrees

•Average height: 40 m

•Number of channels available for WIMAX: 4

•Channel 1: 2500-2506 MHz



•Channel 13: 2572-2578 MHz

•Separation among sites: 3 Km approximately

•Coverage offered: Indoor y Outdoor

•Propagation model: TIREM


Quasi Planning(2)Quasi Planning(2)


Quasi Planning (3)Quasi Planning (3)







6- Link Budget6- Link Budget

Section 6 – Link Budget


DownlinkDownlink

ParameterParameter ValueValue UnitsUnits

BS Power at Antenna Power 35 dBm

BS Antenna Gain (90 deg) 16 dBi

BS Multiple Tx (4) 6 dB

EIRP 57 dBm

SS Antenna Gain 9 dBi

Noise Figure 7 dB

Sensitivity (Includes NF) -96 dBm

System Gain 162 dB


Downlink EnvironmentDownlink Environment

Parameter Value Units

System Gain 162 dB

Fade Margin (4x1 Tx Div) 8 dB

Shadowing 7 dB

Interference 2 dB

Indoor Penetration 12 dB

Path loss margin 133 dB


UplinkUplink


SS Power at Ant. Port 24 dBm

SS Antenna Gain 9 dBi

EIRP 33 dBm

BS Antenna Gain 16 dB

Subchannelization Gain 12 dB

Noise Figure 4 dB

Sensitivity (Includes NF) -99 dBm

System Gain 160 dB


Uplink EnvironmentUplink Environment


Gain 160 dB

Fade Margin (1x4 MRC) 6 dB

Shadowing 7 dB

Interference 2 dB

Indoor Penetration 12 dB

Path loss margin 131 dB


Modulation SchemeModulation Scheme

Modulation Scheme BS (dBm) SS (dBm)

QPSK ½ -95 -94

QPSK ¾ -93 -92

16-QAM ½ -90 -89

16-QAM ¾ -87 -86

64-QAM 2/3 -83 -82

64-QAM ¾ -81 -80

7- Capacity Planning7- Capacity Planning

Section 7 – Capacity Planning


TDDTDD

•TDD is supporting:

•How the base station creates data transmission frames. A frame is the basic unit of data communication. It allows data traffic to travel uplink and downlink over the same channel, without “colliding”.

•How subscribers’ CPEs contend for uplink transmission times (time slots) defined in the frame. After the CPE obtains access to a time slot, the CPE’s data can be transmitted upstream to the base station.

Planning processPlanning process

•Target Market

Segment

•Demographics

•Services•Expected

market

•Morphology Terrain

•Expected Number of Customers

•Required

•Capacity


Capacity calculationCapacity calculation

•Level A 512 Kbps Uplink/ 1024 Kbps Downlink

•Level B 256 Kbps Uplink/ 512 Kbps Downlink

•Level C 128 Kbps Uplink/ 256 Kbps Downlink

Throughput offered

Let's suppose that we know that we will have for the first year 1000 users, that will distribute in 10 % for the level

A, 30 % for the level B and 60 % for the level C. This represents:

•Users level A: 100

•Users level B: 300

•Users level C: 600


Capacity calculation (2)Capacity calculation (2)

Now then, realizing a linear calculation, we might say that demand for bandwidth of users for first year is as continues:

•Uplink= 100 * 512 Kbps + 300*256 Kbps + 600*128 Kbps = 204,800 Kbps

•Downlink=100*1024 Kbps + 300 * 512 Kbps + 600* 256 Kbps = 409,600 Kbps

We are using TDD:

•Total = 204,800 Kbps + 409,600 Kbps = 600 Mbps



Percentage of usage = (Percentage of active users) * (Percentage of average air time usage by active users)

•If user behavior is that just 40% of users will be actived and from that percentage 20% of time will be used:

•Percentage of usage = (0.4) * (0.2) = 0.08 = 8%


Capacity calculation (4)Capacity calculation (4)Replication ratio = 1 / (Percentage of usage) = 1 /( (Percentage of active users) * (Percentage of

average air-time usage) )

Or OSF (Over Subscription Factor)

OSF= 1/0.08 = 12.5



Uplink Capacity Downlink Capacity

8- Optimization Process8- Optimization Process

Section 8 – Optimization Process


RecommendationsRecommendations

• Divide network into cluster

• Compare propagation model in sites at clusters with data field

• Include enough sites in the analysis

• Check your frequency plan in each cluster

• Check number of users and activity user per days and month

• Performance of system

• Interference from CPE’s and BTS’s


CPE and fixed testCPE and fixed test

•CPE

•CPE•CPE

•CPE


•Distribution of users by modulation

9.- WIMAX Mobile9.- WIMAX Mobile


WiMAX IEEE 802.16d and 802.16e parametersWiMAX IEEE 802.16d and 802.16e parametersSection 9 – WiMax Mobile and Beyond

Properties IEEE802.16d IEEE802.16e

Frequency range 2 GHz to 66 GHz 2 GHz to 11 GHz

Modulation BPSK (pilot), QPSK, 16QAM, 64QAM

BPSK, QPSK, 16QAM, 64QAM

Multiple access TDMA, OFDM 256 FFT, OFDMA-SC

Scalable OFDMA 128 to 2048 FFT, TDMA, OFDMA 256 FFT SC

Duplex TDD/FDD TDD/FDD

Channel bandwidth 1.25 MHz to 28 MHz ( in line with local regulations)

1.25 MHz to 28 MHz ( in line with local regulations)

Peak data rate 134 Mbps SC (28 MHz)

75 Mbps OFDM (20 MHz)

15 Mbps OFDM (5 MHz)

Mobility ----------------- 60 Km/h

Guard interval ¼,1/8, 1/16, 1/32 ¼,1/8, 1/16, 1/32

PHY LayerPHY Layer

• Scalable OFDMA

• New frame structure

• Data channels configurations

• Fully used subchannelization (FUSC)

• Partially used subchannelization (PUSC)

• Advanced modulation and coding scheme (AMC)

• Modulation and channel coding

• Smart antennas technologies

Section 9 – WiMax Mobile and Beyond

Section 9 – WiMax Mobile and Beyond

Scalable sOFDMA (1)Scalable sOFDMA (1)

Data carriers

Total Frequency band

Pilot Carriers

Frequency guard Band Frequency Guard Band

Scalable sOFDMA (2)Scalable sOFDMA (2)Section 9 – WiMax Mobile and Beyond

Parameters Value

System channel bandwidth (MHz) 1.25 5 10 20

Sampling Frequency (Fp in MHz) 1.4 5.6 11.2 22.4

FFT size (NFFT) 128 512 1024 2048

Number of subchannels 2 8 16 32

Subcarrier frequency spacing 10.94 KHz

Useful symbol time (Tb = 1/f) 91.4 microseconds

Guard time (Tg=Tb/8) 11.4 microseconds

OFDMA symbol duration (Ts=Tb+Tg) 102.9 microseconds

Number of OFDMA symbols (5 ms frame) 48

Scalable sOFDMA (3)Scalable sOFDMA (3)

bpsratecodeModulationssubchannelofNumbernumberFFT

HzBandwidhtMSRSB )__(*)__(*

_

)(

•Example:

Bandwidth: 1.25 MHz

FFT Number: 128

Number of Subchannels:2

Modulation code rate: ½

MSRSB= (1,250,000/128) * 2 * 0.5= 9.7 kbps

New Frame StructureNew Frame Structure

Defined by IEEE802.16e committee and WiMax Forum

Data channel configurationsData channel configurations

• Downlink vs Uplink: There are three different types of downlink subchannels (FUSC, PUSC and AMC) and two basic for uplink (PUSC and AMC). Patterns for uplink and downlink in PUSC are different.

• Diversity vs Adjacent: Diversity subchannel (PUSC and FUSC) consists of distributed subcarriers and adjacent (AMC) is comprised of consecutive subcarriers.

• Pre-pilot vs post-pilot: Except for FUSC, all subchannel configurations have pilots and data subcarriers together in some fixed units. In FUSC, subcarriers are divided into subchannels after pilot tones are already in their positions.

FUSC (Fully Used Subchannelization)FUSC (Fully Used Subchannelization)

• For an example of 10 MHz and 1024 FFT a DL FUSC contains:

•16 subchannels

•Each subchannel has 48 subcarriers

•Each group consists of 16 contiguous data subcarriers

Bandwidth (MHz)

1.25 5 10 20

FFT size 128 512 1024 2048

No. of guard subcarries (left)

11 43 87 173

No. of guard subcarries (right)

11 43 86 172

No. of data subcarriers

96 384 768 1536

No. of pilot subcarriers

9 42 83 166

No. of data subchannels

2 8 16 32

No. of subcarriers per subchannel

48 48 48 48

PUSC (Partial Used Subchannelization) (1)PUSC (Partial Used Subchannelization) (1)• PUSC DL

• Data subcarriers are partitioned into clusters, each of which contains a total of 28 subcarriers over 2 OFDMA symbol periods. Clusters are then rearranged and partitioned into 6 non overlapping groups, which can be allocated to different sectors all cells.

• Within each group, 48 subcarriers are mapped into subchannels based on permutation mechanism that minimizes probability of hits among groups.

PUSC (Partial Used Subchannelization) (2)PUSC (Partial Used Subchannelization) (2)

DL distributed subcarrier permutation (PUSC)

Parameters Values

System bandwidth (MHz) 1.25 5 10 20

FFT size (N FFT) 128 512 1024 2048

Number of guard subcarriers 43 91 183 367

Number of clusters/subchannels 6/3 30/15 60/30 120/60

Number of used subcarriers 85 421 841 1681

Number of data subcarriers 72 360 720 1440

Number of pilot subcarriers 12 60 120 240

PUSC (Partial Used Subchannelization) (3)PUSC (Partial Used Subchannelization) (3)• PUSC UL

• Basic unit in a UL PUSC is called a tile. Whole frequency band is partitioned into groups of contiguous tiles. Each subchannel consist of 6 distributed tiles, where each tile is chosen from different groups.

• Each tile spans 4 subcarriers over 3 OFDM symbol periods The 4 X 3 tile contains more pilots than the 3 X 3 and, therefore, is more robust. Each subchannel is comprised of 6 tiles, and the exact allocation of tiles into a subchannel is defined by the uplink permutation formula. As always, there is a total of 48 subcarriers in each subchannel.

PUSC (Partial Used Subchannelization) (4)PUSC (Partial Used Subchannelization) (4)

Parameters Values System bandwidth 1.25 5 10 20

FFT size (N FFT) 128 512 1024 2048

Number of guard subcarriers 31 103 183 367

Number of tiles 24 102 210 552

Number of subchannels 4 17 35 92

Number of subcarriers per tile 4 4 4 3

Number of used subcarriers 97 409 841 1681

UL distributed subcarrier permutation (PUSC)

AMC (Adaptive Modulation and Coding Scheme) AMC (Adaptive Modulation and Coding Scheme)

•In both uplink and downlink AMC modes, data subcarriers

are partitioned into bands of consecutive subcarriers.

•Each band has 4 bins, which is a collection of 8+1=9 subcarriers. Depending on how the 6 bins (6X8=48 subcarriers) are arranged into subchannel, there are four types of AMC subchannels.

•This type of DL/UL is used in fixed applications.

Modulation and channel codingModulation and channel coding

•BPSK, QPSK, 16QAM and 64QAM are supported for 802.16e, 64 QAM is optional for uplink.

•Channel coding options include:

•Repetition coding (2x, 4x and 6x) for control signals

•Convolutional coding (CC) with incremental redundancy

•Convolutional turbo coding (CTC) with incremental redundancy

•Block turbo coding (BTC)

•Low-density parity-check coding (LPDC)

Smart antennas technologies (1)Smart antennas technologies (1)

•Beamforming: With beamforming, the system uses multiple-antennas to transmit weighted signals to improve coverage and capacity of the system and reduce outage probability.


•Space-Time Code (STC): Transmit diversity such as Alamouti code is supported to provide spatial diversity and reduce fade margin.


At the receiver, baseband symbols are received with the following noise addition and alteration:

•R0 = h0xS0 + h1xS1 + n0

•R1 = –h0xS1* + h1xS0* + n1

•R2 = h2xS0 + h3xS1 + n2

•R3 = –h2xS1* + h3xS0* + n3

Where h represents the respective channel transfer function and n the respective noise to each antenna.

The receive symbols may be express as:

•Ŝ0 = h0*xR0 + h1xR1* + h2*xR2 + h3xR3*

•Ŝ1 = h1*xR0 – h0xR1* + h3*xR2 – h2xR3*

•Spatial Multiplexing (SM): Spatial multiplexing is supported to take advantage of higher peak rates and increased throughput.


•Quality of Service (QoS) Support

•MAC Scheduling

•Bandwidth allocation and Request Mechanism

MAC DescriptionMAC Description

QoS SupportQoS SupportQoS Category Applications QoS Specifications

UGS

Unsolicited Grant Service

VoIp •Maximum Sustained Rate

•Maximum Latency Tolerance

•Jitter Tolerance

rtPS

Real Time Polling Service

Streaming Audio or Video •Minimum Reserved Rate

•Maximum Sustained Rate


•Traffic Priority

ErtPS

Extended Real Time Polling Service

Voice with Activity Detection (VoIP)

•Minimum Reserved Rate



•Traffic Priority

•Jitter Priority

nrtPS

Non Real Time Polling Service

File Transfer Protocol

(FTP)

•Minimum Reserved Rate


•Traffic Priority

BE

Best Effort Service

Data Transfer, Web, Browsing, etc


•Traffic Priority

MAC SchedulingMAC Scheduling•Deliver of data services in a wireless channel that varies over time

•Fast Data Scheduler. The MAC scheduler must efficiently allocate available

resources in response to bursty data traffic and time-varying channel conditions. The

scheduler is located at each base station to enable rapid response to traffic

requirements and channel conditions.

•Scheduling for both DL and UL: The scheduling service is provided for both DL

and UL traffic. In order for the MAC scheduler to make an efficient resource

allocation and provide the desired QoS in the UL, the UL must feedback accurate

and timely information as to the traffic conditions and QoS requirements.

•Dynamic Resource Allocation: The MAC supports frequency-time resource

allocation in both DL and UL on a per-frame basis. The resource allocation is

delivered in MAP messages at the beginning of each frame.

•QoS Oriented: The MAC scheduler handles data transport on a connection-byconnection

basis. Each connection is associated with a single data service with a set

of QoS parameters that quantify the aspects of its behavior.

•Frequency Selective Scheduling: The scheduler can operate on different types of

sub-channels. For frequency-diverse sub-channels such as PUSC permutation, where

sub-carriers in the sub-channels are pseudo-randomly distributed across the

bandwidth, sub-channels are of similar quality.

Architecture (1)Architecture (1)

• Support for services & applications

• Interworking and Roaming

• Security

• Mobility and Handovers (Handoffs)

• Scalability, Extensibility, Coverage and Operator selection

• Multivendor Interoperability

• Quality of Service

• Specifications Timeline

Architecture (2)Architecture (2)

Mobility SupportMobility SupportSS Serving BS1

Serving BS2

Synchronization with BS1

Searching for neighbouring BS channel measurement, initial ranging

Synchronization with BS2

Initial ranging and network entry

Terminate Service

Neighbouring BS

detected

Link Budget (1)Link Budget (1)

•Link Budget for DL, Vehicular

Link Budget (2)Link Budget (2)

•Link Budget for DL, Vehicular

End of CourseEnd of Course

WiMax Applied Radio Network Planning

Documents

smart antennas technologies

transmit power

spatial multiplexing

coding scheme

section 3 physical

guard subcarries

mac layers

capacity calculation