STG(10)27 - OFDMA WiMAX algorithm

8/7/2019 STG(10)27 - OFDMA WiMAX algorithm

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ECCElectronic Communications Committee

CEPT

STG(10)27

STG #22WGSE - SEAMCAT Technical GroupECO, Copenhagen18 May 2010

Date Issued: 03 May 2010

Source : ECO

Subject: WiMAX specification in SEAMCAT

Document: for discussion

Summary Extensive discussion between ECO and SAMSUNG/INTEL WiMAXs expert has lead to thedrafting of this document.

UL power control still need further specifications.

Proposal STG is invited to consider the following specifications and to give feedback.

Background OFMDA LTE module has been implemented in SEAMCAT. WiMAX is now to beimplemented in SEAMCAT has planned.


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OFDMA WiMAX Algorithm - draft

Below is a draft of the specification to the implementation of WiMAX in SEAMCAT.General assumption:

It is assumed that FDD WiMAX will be implemented in SEAMCAT, as a first phase.Implementation of TDD will need further documentation. It is the 802.16e.

A load of 100% is assumed.

1 GENERAL FLOW - SIMULATION PROCEDURE FOR WIMAX

A. Parameters setup - Configure system deployment layout and simulation parameters.

i. Parameters for cell radius, RF configuration (TX power, antenna pattern, pathossmodel, shadowing, penetration loss, etc.) are set up. (new inputs)

ii. Parameters for simulation (total number of snap-shots, number of MS per sector,number of active MS which represents the number of MS scheduled at once withequal resource amount). It is assumed that each sector has exact the samenumber of simultaneously active MS in each snap-shot throughout thesimulation. (re-use)

B. BS location - Place subscriber stations in the service area with the selected base station

deploymenti. Cell layout configures 19 cells of 2 tiers as the ideal type. Each cell is composed

of 3 sectors. (re-use) with wrap arround is already implementedii. Frequency reuse of 1 .

C. MS distribution (re-use)

i. A large amount of MSs is randomly placed (40 Ues in each sector) with uniformdistribution over the whole service area for every snap-shot.

ii. The necessary parameters are calculated between all sectors and each MS suchas path loss, shadowing, penetration loss, and antenna gain. The best server(sector) for each MS is determined according to the SINR derived from thecalculated parameters. At this stage only intra-system interference is considered.

iii. If any sector has less than 5 (as an example in this contribution) associated MS,go back to Step i.

iv. For each sector, randomly choose 5 MS as simultaneously active MS among itsentire associated MS for this event.

D. SINR calculation (new equations see Table 4 and Table 5 )

i. SINR for an MS is calculated considering interference from both intra-system/co-channel (i.e. same system-adjacent cell) and inter-system (i.e. externalinterference).

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ii. BS and MS are assumed to transmit at its maximum power .

For DL it is assumed that the BS transmit at maximum power.

At the time of the drafting of the specification, a typical UL power control wasnot available for 802.16e. Therefore, for the first phase of theimplementation, the LTE power control will be kept to allow flexibility to thetool. Nevertheless, If the SEAMCAT user wants to use full power transmissionat the UE _as recommended by the WiMA X experts, he can select the min andmax of MS to the same value. The min and max value will be set by default tothe same value when WiMAX is selected until the WiMAX community providesspecifications.

The WiMAX UL power control algorithm will be provided in the future by the

WiMAX community. use ECC PT1 document algorithm. Further discussionmay be required, in order to optimize the speed of the PC. Currently, with 150

repetition, it may cause a burden to the simulation time.

If further power control of WiMAX uplink is considered optionally, IEEE802.16m [2] open loop power control could be considered as defined insection 6 . (802.16m is the advanced version of 802.16e)

E. Modulation efficiency calculation

F. Results collectionLTE WiMAX

Bit rate loss Modulation efficiency (new)Outage (i.e. Loss of users) (new)Bit rate loss need link level mapping

as a first stage the LTE curves will be used.

Table 1: Summary of the ouput results for LTE and WiMAX

G. Repeat Steps C to F until the number of snap-shots is reached.

2 INPUT PARAMETERS

2.1 Deployment parameters

Input Description Comment forimplementation

Cell layout Macro 19 clover-leaf cells, 3sectors per cell

re-use (omni will bedisabled) it could bepossible to also useomni in WiMAX

Cell size Radius: R = 1 000 m re-useSpectrum band 2.500 ~ 2.690 GHz re-use

Allocatedbandwidth 5 MHz

re-use

802.16 systemload 100%

In LTE, full load isassumed

Active users 5 per sector (nomadic), 1 In LTE, it is the ratio of

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per sector (fixed) Afterdiscussion with Xinrong, it ispossible to reuse the LTEinputs, i.e. It may not beneeded to have a an extrafield

the RBs at the BS andMS

Power control

No power control in 802.16eat the time of drafting.WiMAX UL power controlalgorithm will be provided inthe future.

Set min and max valueof the existing LTE PCto the same value.

Base stationantenna type Directional

re-use

Frequency reuse(802.16) 1 3 1,

Frequency re-use of 1

UE locations Uniformly distributed re-use

UEantenna type Omnidirectional re-use

Minimum couplingloss betweencollocated basestations

50 dB Note that thiscoupling loss is larger thanthat given in ReportsITU-R M.2030 and (ITU-RM.2116); however it lieswithin the range of improved coupling lossesgiven in Report ITU-RM.2045.

re-use changedefault value

Table 2: Common simulation assumptions and parameters ([1])

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WiMAX parameters

BS MS Comment forimplementation

Max TX power(dBm)

36 24 (fixed)20 (nomadic)

re-use

Antenna gain(dBi)

18 8 (fixed)3 (nomadic)

re-use

Antenna height(m)

30 4 (fixed)1.5 (nomadic)

re-use

ACLR @ 5 MHz(dB)

53.5 37 (fixed)33 (nomadic)

Spectrum mask isused. ACLR can be

extracted forinformation (see note)

ACLR @ 10 MHz

(dB)

66 51 Spectrum mask is

used. ACLR can beextracted forinformation (see note)

ACS @ 5 MHz )(dB) 70 40 re-useACS @ 10 MHz(dB)

70 59 re-use

Noise figure (dB) 3 5 re-use

Table 3: 802.16 FDD parameters (Editors note: this table is originally extractedfrom TDD material ([1]), FDD value need to be check see WiMAX representative in

CEPT see ECC PT1(10)065 annex 08 -- Wimax Forum 100301)

Note: In SEAMCAT, the ACLR is only given as information since the spectrum mask is the inputparameter. With the ACLR conversion implemented in SEAMCAT, it is easy for the user to set aspectrum mask so that it fits the desired ACLR.

3 SINR MODELLING

SINR is given by:

++=

==10

1

10

1

1010 101010log10

,, N n

j

I n

i

I A jAC iC

S SINR

NF BW N ++= )Hzin(log10174 10

where S is the desired signal strength (dBm) at the receivern C: number of co-channel interfering transmissions (i.e. number of interfering

links)

IC,i: co-channel interference received from the ith transmitter (dBm)

n A: number of adjacent channel interfering transmissions

IA,j: adjacent channel interference received from the jth transmitter (dBm) asreduced by the ACS and ACLR

N: thermal noise (dBm)

NF : system noise figure (dB).

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For co-channel coexistence studies, the adjacent channel interference term in the aboveequation is ignored.

3.1 Intra-system/Co-channel Interference in DLFrequency reuse 1 3 1: co-channel interference from downlinks of other sectors of thesame cell and downlinks of other cells of the same system. (existing)

3.2 Intra-system/Co-channel Interference in UL

Frequency reuse 1 3 1: co-channel interference from uplinks of other sectors of thesame cell and uplinks of other cells of the same system. (existing)

3.3 Inter-system to WiMAX / external interference to WiMAX

Within the WiMAX community, the ACLR and ACS methodology is considered. If the inter-system interference comes from adjacent channel, it is reduced by ACIR (ACIR=(1/

(1/ACLR+1/ACS)) in linear scale). ACLR is the adjacent channel leakage ratio defined as theratio between the power of in-band channel and the power of adjacent channel. ACS is adjacentchannel selectivity defined as the ratio of the attenuation of the receiver filter in its ownchannel to the attenuation of the receiver filter in the adjacent channel. ACIR is modelled asflat in receivers bandwidth of victim systems, i.e. the same value of ACIR is used for allresource assigned to MS.

This approach is very similar to what was done in 3 GPP, in SEAMCAT, the ACLR and ACS is notconsider. Instead the unwanted and the blocking calculations are performed.

Table 4 and Table 5 summarises the comparison of the SINR calculation in SEAMCAT betweenLTE and WiMAX for DL and UL respectively. This eases to identify the similarities for theimplementation of mobile WiMAX in SEAMCAT.

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Directio

n

LTEWiMAX

Frequency reuse: 1x3x1

DL For WiMAX DL interferer: The carrier frequency of the WiMAX system is used as specified by the SEAMCAT user (i.e. f 1

in the illustration below), the spectrum mask is defined over the whole (5MHz) system bandwidth (ACLR can be

extracted from the preview feature in SEAMCAT). It is the same whether it is 1x3x1 or1x3x3 frequency re-use scheme.

The Tx power of the BS is scaled to the number of served UEs (see below)

5 UEs are sharing the whole bandwidth 5 MHz.

BW = X MHz per sector BW = XMHz per sector

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Full load system is assumed (i.e. allavailable RBs will be allocated to activeUEs) Each UE is scheduled with the samenumber N of RBs. Thus, the BS transmitpower per UE is fixed.Let MaxBS P denotes the max. transmitpower of BS

K N M = is the number of all availableRBs in each cell

UE BS P is the transmit power from BS to the

active UE,

M N P P MaxBS

UE BS = .

UE BS P is the transmit power from BS to the active UE (i.e. active link). The frequency re-use does

not impact the calculation of UE BS P , i.e. same equation whether it is 1x3x1 or 1x3x3.

UE

MaxBS UE

BS N P

P =

where MaxBS P denotes the maximum transmit power of the BS (in dBm) and N UE is the number of

active UE served by a BS. Note that MaxBS P is specified as input parameter to SEAMCAT.

Calculate DL C/I for all active UEs in allcells.Loop over all cells from 1=j to cell N (the number of cells in the system areae.g. 57 for 19 sites with tri-sectorantennas)

Loop over all active UEs from 1=k to K

),(),(

/k jI k jC

I C =

Calculate DL C/I for all active UEs in all cells.Loop over all cells/sectors from j=1 to n c = N cell x N sector (where Ncell is the number of cells in thesystem area e.g. 19 and Nsector is the number of sectors per cell e.g. 3) and loop over all active UEsper sectors from k=1 to NUE (in this example NUE = 5 )

++= ==

10

1

10

1

1010 101010log10

,, N n

j

I n

i

I A mAC iC

S SINR

( )I S SINR 10log10=

where S = C(j,k) which is the desired received signal from the j-th BS to its served k-th UE

),(_ ),( ,k jjUE

BS UE BS pathlosseffectiveP k jC = C(j,k) is the same whether a frequency re-use of 1x3x1 or 1x3x3 is considered. It is defined as),(_ ),( ,k jj

UE BS UE BS pathlosseffectiveP k jC =

where( )MCLGGpathlossRxTxpathlosseffective RxTx ,max),(_ =

t ext inter N k jI k jI k jI ++= ),(),(),( The interference I is defined as10

1

10

1

10 101010,, N n

m

I n

i

I A mAC iC

I ++= ==

which is equivalent tot ext inter N k jI k jI k jI ++= ),(),(),(

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I = I(j,k) which is the total interfering signal to the link from the j-th BS to its served k-th UE,where Iinter is the co-channel interference i.e. interference from its own system ( Ic) and Iext is theexternal source of interference (IA) and the thermal Noise Nt .

=

=cell N

jl l

UE BS er nt i BpathlosseffectiveP k jI

,1

(_ ),(

Note: the term inter-system interferencein LTE has a different meaning than inWiMAX. It is equivalent to the co-channelinterference term in WiMAX

=

=C n

iiC er I I

1,int

which is equivalent to

= =

=cell tor N

q

N

l l qC er I I

1 1,,int

sec

where( )MCLGGpathlossP I RxTxUE BS l qC l q ,max

,,, =

whereUE

BS l qP , is the transmit power from the BS transmitter (in dBm) of the q-th cell and l-thsector to the its serving UE, GTx is the antenna gain (in dBi) of the BS, GRx is the antenna gain (indBi) of the UE and MCL is the minimum coupling loss as specified by the SEAMCAT user. Note thatthe antenna pattern effect from the BS to the victim UE is included. This effect is different fordifferent victim BS UE combination since the locations are different.

n c = N cell x N sector and is dependent on the frequency re-use scheme as defined below:

co-channel interference from downlinks of other sectors of the same cell and downlinks of all thesectors of other cells of the same system. (See illustration above)

For a tri-sector case (i.e. total BSs = 57):

n c = 56.

in other words, the co-channel interference experienced by the active link victims of the sector x of cell y can be written as

= == =

== +== cell tor ycell tor N

yqq

N

l l qC

N

yq

N

xl l l qC

er ycell xtor I I I

,1 1,,

,1,,

int,sec

secsec

here Ncell = 19 and Nsector =3.

),(),(1

,

_ N

mk jmunwanted ext UE BS iRSS k jI

cell External

=

=OFDMA WiMAX DL as victim:

=

=An

mmAext I I

1,

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where( ) ( )k jmblocking k jmunwanted mA UE Ext iRSS UE Ext iRSS I ,,, ,, =

n A is the number of interferers and is equivalent to the Nexternal_cell of LTE

(),( , t over iRSS UE BS iRSS unwanted k jmunwanted = Where ),( , k jmunwanted UE Ext iRSS is the amount of interference from Ext m into the active link k-thUE connected to its j-th BS (similar to ACLR)

UE tor

unwanted k jmunwanted N N

iRSS UE Ext iRSS = sec,

),(

where iRSS uwanted is the amount of interference over the whole victim system bandwidth (specifiedby the SEAMCAT user) and N UE is the number of victim WiMAX users connected to a BS (in yourexample, N UE = 5). N sector is dependent on the frequency re-use scheme.

For a 1x3x1, N sector = 1

Note: when the Ext are the BSs from WiMAX or LTE, it is all the BSs (e.g. 57 in tri-sector case) of the whole interfering networks.

(equation below expressed in linear scale)whereiRSS unwanted = P BSUE interferers x emission it x effective_pathloss(BS ext ->UE victim )if the interfering links are considered in the calculation. P BSUEinterferers is the interfering power fromthe interfering BS to its serving UE interferers , i.e. P BSUEinterferers = P BS/NUEinterferers .oriRSS unwanted = P BS x emission it x effective_pathloss(BS ext ->UE victim )if the BS (only) is considered. P BS is full power in this case

and where emission it is the interference power integrated in the victim bandwidth (i.e. spectrumemission mask).

syover iRSS UE BS iRSS blocking k jmblocking = (),( , Where ),(, k jmblocking UE Ext iRSS is the amount of interference resulting from the blocking effect

(similar to ACS) from the Ext m into the victim k-th UE connected to its j-th BS

UE sector

blocking k jmblocking N N

iRSS UE Ext iRSS

=),( ,

where iRSS blocking is the amount of interference at the victim frequency and N UE is the number of victim WiMAX users connected to a BS. N sector is dependent on the frequency re-use scheme.

For a 1x3x1, N sector = 1

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(10log10174((^10t N of bandwithN +=tor N

Bandwidt SystemBW

sec

_ =

where System_Bandwidth is specified by the SEAMCAT user where N sector is dependent on thefrequency re-use scheme.

For 1x3x1, N sector = 1BW = 5 MHz

NF BW N ++= )Hzin(log10174 10Table 4: Comparison of the SINR calculation in SEAMCAT between LTE and WiMAX for DL

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direction

LTEWiMAX

Frequency reuse: 1x3x1

UL The LTE UL MS transmit over a bandwidthdefined by the number of RBs and at acarrier frequency calculated based on thethe number of MS so that blocks of subcarriers are made.

For WiMAX UL interferer: The carrier frequency of the WiMAX system is used as specified by the SEAMCAT user, the spectrum mask over the whole (5MHz) system bandwidth is used (ACLR can be

extracted from preview in SEAMCAT) and is the same whether it is 1x3x1 or 1x3x3frequency re-use scheme.

The Tx power of the UE is the same as specified by the SEAMCAT user (subject to PC)

5 UEs are sharing the whole bandwidth 5 MHz.

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,(_ ),(),( , k jt BUE pathlosseffectivek jP k jC =

where Pt is the transmit power of the UE indBm as input to SEAMCAT (subject topower contol)

Calculate UL C/I for all active UEs in the cells.Loop over all cells/sectors from j=1 to n c = N cell x N sector (where Ncell is the number of cells in thesystem area e.g. 19 and Nsector is the number of sectors per cell e.g. 3) and loop over all active UEsper sectors from k=1 to NUE (in this example NUE = 5 )

++=

==

10

1

10

1

1010 101010log10

,, N n

m

I n

i

I A mAC iC

S SINR

( )I S SINR 10log10=

where S = C(j,k) which is the desired received signal from the k-th UE into the j-th BS. C(j,k) isthe same whether a frequency re-use of 1x3x1 or 1x3x3 is considered. It is defined as

),(_ ),(),( , jk jt BS UE pathlosseffectivek jP k jC =

where Pt is the transmit power of the UE (in dBm) as specified by the SEAMCAT user (subject topower contol).

t ext inter N k jI k jI k jI ++= ),(),(),( The interference I is defined as10

1

10

1

10 101010,, N n

m

I n

i

I A mAC iC

I ++= ==

which is equivalent tot ext inter N k jI k jI k jI ++= ),(),(),(

I = I(j,k) which is the total interfering signal to the link from the k-th UE to j-th BS, where Iinter isthe co-channel interference i.e. interference from its own system ( Ic) and Iext is the interferenceresulting from an external source of interference ( IA) and the thermal Noise Nt .

=

=cell N

jl l

t inter pathlosseffectivek l P k jI ,1

_ ),(),(

where Iinter is the interference coming fromUEs of the same system but from adjacentcells (i.e. the inter-system interferencefrom other cells). Since a fully orthogonalsystem is assumed, only UEs whichtransmit in the same frequencysubcarriers will introduce interference toeach other, hence only UEs in other cellswith the same k index are considered .

=

=C n

i

iC er I I 1

,int

which is equivalent to

= = =

=cell tor UE N

q

N

l

N

r r l qC er I I

1 1 1,,,int

sec

( )MCLGGpathlossP I RxTxt l qC ,max,, =where t P is the Tx power from the UE in dBm as input to SEAMCAT (subject to power contol). n c is the number of UEs from the same system causing co-channel interference ( n c = N cell x N sector x NUE) is dependent on the frequency re-use scheme as defined below:

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co-channel interference from uplinks of other sectors of the same cell and uplinks of other cells(and sectors) of the same system.

=

= = === =

ycell tor UE N

yq

N

xl l

N

r r l qC

er ycell xtor I I

sec

,1 1,,,

int,sec

= = =+

1

,1 1 1,,,

seccell tor UE N

yjq

N

l

N

r r l qC I

where Ncell =19, Ncell=y = 1, Nsector =3 and NUE =5.

= ==cell External N

m

K

vmblocking ext BUE iRSS k jI _

1 1, ,(),(

==An

mmAext I I

1,

where

==

K N

mk jmunwanted k jmblocking ext

cell External

BS Ext iRSS BS Ext iRSS k jI _

1,, ),(),(),(

where n a is the total number of external interferer. If the interferer is cellular, it is equivalent ton a = K x N UE where K is the number of UEs in the interfering cells and Nexternal_cell which is the numberof interference cells (the number of sectors are included)

Unwanted: OFDMA WiMAX UL as victim:Where ),( , k jmunwanted BS Ext iRSS is the amount of interference from Ext m into the victim link j-th BSand its serving k-th UE.

UE tor

unwanted k jmunwanted N N

iRSS BS Ext iRSS = sec,

),(

where iRSS uwanted is the amount of interference over the whole victim system bandwidth and NUE isthe number of victim WiMAX users connected to a BS. When calculating the adjacent channelinterference, each victim UE only get its own portion of adjacent channel interference. Forexample, if the total adjacent channel interference to the whole 5MHz bandwidth is I_total, theneach user only get 1/5 of I_total since each desire user only uses 1/5 of the subcarriers.Nsector is dependent on the frequency re-use scheme (see below).

Note: When Ext m is a UE from WiMAX or LTE, it is all the UEs of the whole interfering network.

(equation below expressed in dB scale)pathlosseffectiveemissionP iRSS it t unwanted _ += where emission it is the interference power integrated

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in the victim WiMAX system bandwidth.

For 1x3x1, N sector = 1.

Blocking calculated at the interferingfrequency using the ACS value

where ),( , k jmblocking BS Ext iRSS is the blocking value calculated at the interfering frequency usingthe ACS value as specified by the SEAMCAT user.

UE sector

blocking k jmblocking N N

iRSS UE Ext iRSS

=),( ,

where iRSS blocking is the amount of interference at the victim frequency and N UE is the number of victim WiMAX users connected to a BS. It is defined as(equation below expressed in dB scale)

ACS pathlosseffectiveP iRSS t blocking

= _ The ACS UL is the value for the whole system, therefore since each of the interfered links in the ULdirection are only a fraction of the used bandwidth, therefore the equivalent ACS for one linkshould also be a fraction it.

Nsector is dependent on the frequency re-use scheme.

For 1x3x1, N sector = 1.(10log10174((^10t N of bandwithN +=

UE tor N N Bandwidt System

BW

=sec

_

where System_Bandwidth is specified by the SEAMCAT user (i.e. in this example 5 MHz) where N UEis the number of victim WiMAX users connected to a BS (in your example, it is 5). N sector isdependent on the frequency re-use scheme.

For 1x3x1, N sector = 1.NF BW N ++= )Hzin(log10174 10

Table 5: Comparison of the SINR calculation in SEAMCAT between LTE and WiMAX for UL

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4 FREQUENCY REUSE SCHEME

Frequency reuse schemes of 1 3 1 and 1 3 3 in the WiMAX system are shown in Figure3.

Figure 3. Frequency reuse schemes 1 3 1

Following is how frequency reuse schemes (1 3 1) and loading factor (100%) are defined.For frequency reuse 1 3 1, each sector in the whole service area uses the same 5 MHz (asan example) bandwidth. Each sector independently and randomly chooses 100% sub-carrierswithin the whole 5 MHz bandwidth as this sectors active sub-carriers. Each sector has five (asan example) simultaneously active users. Each sector evenly and randomly divides its activesub-carriers between users.

In the simulation model, no matter how much bandwidth a BS or a UE occupies, it alwaystransmits at its maximum power. In other words, the power is transmitted on those carriersthat are used.

At any given instance there is only one active user per sector in the 802.16 (fixed). It occupiesthe whole bandwidth and transmits at its maximum power. For 802.16 (nomadic), there arefive active users per sector at any given time. Each user occupies one fifth of the wholebandwidth and transmits at its maximum power. Users are uniformly distributed in the servicearea. For example, in the 131 nomadic case, 100% of the base station power is distributedover 100% of the carriers, and 100% of the UE power is distributed over 1/5 of the carriers.

5 MODULATION EFFICIENCY CALCULATION

In the simulations, after each simulation of a snap-shot SINR at each WiMAX receiver iscollected.

In order to get WiMAX system level performance, WiMAX link level performance results have tobe obtained. The following table shows an example of the WiMAX link level performancesimulation results in AWGN.

Editors note: In other words, there is a direct mapping of the SINR calculated and the SNRused to evaluate the modulation efficiency. Meaning that _as an example_ if for one link aSINR of 5.2 dB is calculated then it is equal to a SNR of 5.2 dB which gives a MEi = 1.5.

WiMAX physical layer is modeled. Neither ARQ nor scheduler gain (multi-user diversity) isincluded. The following table gives the required SNR to achieve the corresponding coding and

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modulation schemes for 1% packet error rate (PER) of 100 bytes convolutional turbo-coded(CTC) packets. Each result is averaged over 10,000 packets.

Outage is subsequently evaluated for WiMAX. Outage occurs when the link SINR drops below 5.88 dB. (Editors note: In LTE, there was no outage of MS. This is new output results. STG willconsider whether it is needed or not)

Note that this table could be changed according to transmission environments such as channeltype, downlink or uplink transmission. This value is dependent on channel, systemconfiguration, etc. Therefore, the SEAMCAT user will be able to fill in the table.

SNR Modulationefficiency relativeto 1/2 rate-coded

QPSK

QPSK CTC ,6 5.88 1/6QPSK CTC ,4 4.12 1/4QPSK CTC ,2 1.1 0.5QPSK CTC 1.9 1

QPSK CTC 5.2 1.516-QAM CTC 7.2 2

16-QAM CTC 11.6 364-QAM CTC 2/3 15.6 4

64-QAM CTC 17.3 4.5

Table 6: Signal to noise ratio and modulation efficiency of WiMAX

physical layer for 1% PER

The WiMAX average modulation efficiency is calculated based on each links SINR and the SNRvalues in the above table, assuming that the interference is noise-like. It is given by:

N

ME

ME

N

i

i== 1

where:MEi: modulation efficiency of the ith link

N: number of total links.

The loss in the modulation efficiency is calculated by:

singleME

multiME1ME_loss =

where:singleME : average modulation efficiency of the WiMAX system without inter-system

interference

multiME : average modulation efficiency of the WiMAX system when coexisting withan interfering system.

Modulation efficiency of 5% or 10% could be used as the system performance protectioncriteria.

(Editors note: In order to get the bit rate loss, like in LTE, there is a need to have mappingeither from SINR -> bitrate or modulation efficiency bitrate.)

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Xinrong: We can provide spectral efficiency vs SNR curves in the future if needed. Actuallyspectral efficiency loss is equivalent to modulation efficiency loss.

6 UL POWER CONTROL OPTIONAL

TO BE DISCUSSED FURTHER

WiMAX UL power control (extracted from ECC PT1(10)065 annex 08 -- WimaxForum 100301)

Power control in a mobile WiMAX MS is a mandatory feature identified in the Mobile WiMAXspecification [19] and is detailed in the IEEE 802.16 [18].

Under normal operational conditions, the WiMAX MS determines its TX power by the followingequation,

P(dBm) = L + C N + NI + Offset_SSperSS + Offset_BSperSSwhere,P is the TX power level (dBm) per a subcarrier for the current transmission, including MSTX antenna gain;L is the estimated average current UL propagation loss. It shall include MS TX antenna

gain and path loss, but exclude the BS Rx antenna gain;C/N (new input field - table) is the target C/N of the modulation/FEC rate for the currenttransmission. Note that it includes the number of repetitions for the modulation/FEC rate;NI is the estimated average power level (dBm) of the noise and interference per a

subcarrier at BS, not including BS Rx antenna gain;Offset_SSperSS is the correction term for UE-specific power offset. It is controlled by UE. Its

initial value is zero; (to be hard coded to zero in SEAMCAT)Offset_BSperSS is the correction term for UE-specific power offset. It is controlled by BS

with power control messages.

In the simulation, target C/N including R is provided in Table 6 . Initially, BS decides each MSssuitable UL target C/N by its reported DL CINR.

C/N_target = 10 log 10 (max(SINR min , IoT CINR DL-0.5)).

where,SINRmin (new input field) is the minimum UL SINR target of the system in linear scale, decidedby BS; IOT (new input field) is the fairness and IoT control factor, which is between 0.1 and 0.4;

CINRDL is the MSs DL CINR in linear scale, which is measured by MS and to be reported to BS.

Following is the UL power control procedure in the simulation.

Step 1: BS decides MSs MCS level by using the calculated C/N_target and Table 13.1.This operation is done only once per event for each UEs (equally called MSs)This means that each MS has its own CINR DL value so that:

CINRDL_i = (P BSmax /NUE)x effective_pathloss(BS,UE i) (1)Note that for the UL case, the knowledge of the BS transmit power is then also necessary (Newfield).

The C/N_target can be calculated for each of the UEs so that for UE i the correspondingC/N_target i is defined as:

C/N_target i = 10 log 10 (max(SINR min , IoT CINR DL_i-0.5)). (2)Where i-th is the index of the UE.

The C/N_target = SNR of table 6.

Example: if for UE 1 connected to Cell1-BS1, the C/N_target 1 = 7.2 dB, then this means that UE 1will be associated with a 16-QAM CTC and a Modulation efficiency ME = 2

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Step 2: MS starts with a certain power level by WiMAX power control equation.PUEi = Tx power +G UEi= L + CN_target i + NI + Offset_SSperSS + Offset_BsperSS (3)

Where: L = Pathloss(BS,UE i) + G UEi where GUEi is antenna gain at the UEi and Pathloss(BS,UE i) is

the pathloss between the BS and the connected UEi. CN_target i is calculated from step 1 . NI is the estimated average power level (dBm) of the noise and interference per a

subcarrier at BSo When WiMAX is interferer:NI = ?o When WiMAX is victim:NI = ?

Offset_SSperSS = 0 dB Offset_BsperSS = 0 dB

Therefore equation (3) can be rewritten such as:

PUEi = Tx power +G UEi= Pathloss(BS,UE i) + G UEi + CN_target i + NI + Offset_SSperSS +Offset_BsperSS (4)

The GUEi can be removed which simplifies the equation in:PUEi = Tx power = Pathloss(BS,UE i) + CN_target i + NI + Offset_SSperSS + Offset_BsperSS

(5)

Note: In Step 2, P UEi is equivalent to P min .

Step 3: Each MSs UL, the SINR at the BS is calculated, including interference from the othersystem.

++=

==

10

1

10

1

1010 101010log10

,, N n

m

I n

i

I BS

UE BS

UE

A mAC iC

iiS SINR (6)

Step 4: If MSs UL SINR is lower than its MCS required SINR and the MS still has enough powerroom, the MS will increase its TX power by 0.5 dB by setting Offset_BSperSS value.

Question: how do you quantify the enough power room ? I am calling it here P max

If (SINR UEiBS < C/N_target && PUEi < P max ){Offset_BsperSS = Offset_BsperSS + 0.5;PUEi = Tx power = Pathloss(BS,UE i) + CN_target i + NI + Offset_SSperSS + Offset_BsperSS

}

Step 5: If MSs UL SINR is higher than or equals to its MCS required SINR plus 0.5 dB and theMSs TX power is not less than minimum TX power plus 0.5 dB, the MS will reduce its TXpower by 0.5 dB by setting Offset_BSperSS value.

If (SINR UEiBS C/N_target + 0.5 && PUEi > P min +0.5){Offset_BsperSS = Offset_BsperSS - 0.5;PUEi = Tx power = Pathloss(BS,UE i) + CN_target i + NI + Offset_SSperSS + Offset_BsperSS

}

Step 6: Go to step 3. Repeat 150 steps in the simulations, and then collect statistics.Calculate SINR UEiBS using the final P UEi

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7 REFERENCES

[1] Report ITU-R M.2113-1, Report on sharing studies in the 2500-2690 MHz band between IMT-2000 and fixed broadband wireless access systemsincluding nomadic applications in the same geographical area

[2] IEEE 802.16m document, IEEE 802.16m Evaluation Methodology Document (EMD)

Documents

STG(10)27 - OFDMA WiMAX algorithm