LTE Link Budget

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  1. Introduction The initial planning of any Radio Access Network begins with a Radio Link Budget. As the name suggests, a link budget is simply the accounting of all of the gains and losses from the transmitter, through the medium (free space, cable, waeguide, fiber, etc.! to the receier in a telecommunication system. n this page, we will briefly discuss link budget calculations for LT#. 2. LTE Radio Link Budgeting 2.1. Typical Parameter Values The link budget calculations estimate the maximum allowed signal attenuation g between the mobile and the base station antenna. The maximum path loss allows the maximum cell range to be estimated with a suitable propagation model. The cell range gives the number of base station sites required to cover the target geographical area.The following table shows typical (practical) parameter values used for doing an LTE adio Link !udget.  ParameterTypical Value a !ase tation maximum transmission power. # typical value for macro cell base station is $%&'  at the antenna connector.*+ , *- d!m b !ase tation #ntenna ain/anufacturer 0ependent c 1able loss between the base station antenna connector and the antenna. The cable loss value depends on the cable length2 cable thickness and frequency band. /any installations today use 3 heads where the power amplifiers are close to the antenna making the cable loss very small.4 , ' d! d !ase tation E562 1alculated as # 7 ! & 1   e 8E 3 noise figure. 0epends on the frequency band. 0uplex separation and on the allocated bandwidth.' , 44 d! f  Terminal noise can be calculated as9: K (Boltzmann constant) x T (290K) x bandwidth ;.The bandwidth depends on bit rate2 which defines the number of resource blocks. e assume <% resource blocks2 equal  /=>2 transmission for 4 /bps downlink.&4%*.< d!m for <% resource blocks ( /=>) g 1alculated as E 7 3   h ignal&to&noise ratio from link simulations or measurements. The value depends on the modulation and coding schemes2 which again depend on the data rate and the number of resource blocks allocated.& to &? d! i 1alculated as  7 =    j 5nterference margin accounts for the increase in the terminal noise level caused by the other cell. 5f we assume a minimum &factor of &* d!2 that corresponds to 4%@Log4%(474%A(*B4%)) C <.< d! interference margin.+ , - d! k 1ontrol channel overhead includes the overhead from reference signals26!1=2 6011= and 6=51=.4% , $< D  = %.* , 4.% d! L 8E antenna gain./anufacturer 0ependent M !ody loss 0evice 0ependent  2.2. Uplink Budget The table below shows an example LTE link budget for the uplink from 4F2 assuming a '* kbps data rate and two resource block allocation (giving a +'% k=> transmission bandwidth). The 8E terminal power is assumed to be $* d!m (without any body loss for a data connection). 5t is assumed that the eGode ! receiver has a noise figure of $.% d!2 and the required ignal to Goise and 5nterference atio ( 5G) has been taken from link level simulations performed in 4F. #n interference margin of $.% d! is assumed. # cable loss of $ d! is considered2 which is compensated by assuming a masthead amplifier (/=#) that introduces a gain of $.% d!. #n H antenna gain of 4-.% is assumed considering a +&sector macro&cell (with '<&degree antennas). 5n conclusion the maximum allowed path loss becomes 4'+.* d!. 8plink Link !udget for '* kbps with dual&antenna receiver base station  Data rate (kbps)64 Transmitter – UE    a /ax. TH power (d!m)$*.% b TH antenna gain (d!i)%.% c !ody loss (d!)%.% d E56 (d!m)$*.% C a 7 b 7 c   Receier – e!ode B   e Gode ! noise figure (d!)$.% f  Thermal noise (d!m)&44-.* C k(  !olt>mann  ) * T (  $%I  )* ! (  +'%k=>  ) g eceiver noise floor (d!m)&44'.* C e 7 f  h 5G (d!)&?.% 3rom imulations performed in 4F i eceiver sensitivity (d!m)&4$+.* C g 7 h  j 5nterference /argin (d!)$.% k 1able Loss (d!)$.% l H antenna gain (d!i)4-.% m /=# gain (d!)$.%   axim#m $ath loss 16!4 d # i # j # k $ l % m   The table below shows an example LTE link budget 2.3. o!nlink Budget The table below shows an example LTE link budget for the downlink from 4F2 assuming a 4 /bps data rate (assuming antenna diversity) and 4% /=> bandwidth. The eGode ! power is assumed to be *' d!m2 a value typical among most manufacturers. #gain the 5G value is taken from link level simulations performed in 4F. # + d! interference margin and a 4 d! control channel overhead are assumed2 and the maximum allowed path loss becomes 4'<.< d!. 0ownlink Link !udget for 4 /bps with dual&antenna receiver terminal   Data rate (Mbps)1 Transmitter – e!ode B   a = &0 1= power (d!m)*'.% b TH antenna gain (d!i)4-.% c 1able loss (d!)$.% d E56 (d!m)'$.% C a 7 b 7 c    Receier – UE    e 8E noise figure (d!)?.% f  Thermal noise (d!m)&4%*.< C k(  !olt>mann  ) * T (  $%I  )* ! (  +'%k=>  ) g eceiver noise floor (d!m)&?.< C e 7 f  h 5G (d!)&4%.% 3rom imulations performed in 4F i eceiver sensitivity (d!m)&4%?.< C g 7 h  j 5nterference /argin (d!)+.% k 1ontrol 1hannel Jverhead (d!)4.% l H antenna gain (d!i)%.% m !ody Loss (d!)%.%   axim#m $ath loss 16&!& d # i # j # k $ l % m The table below shows an example LTE link budget 2. . Propagation #Pat$ Loss% &odels  # propagation model describes the average signal propagation2 and it converts the maximum allowed propagation loss to the maximum cell range. 5t depends on9  Environment 9 urban2 rural2 dense urban2 suburban2 open2 forest2 seaK  0istance  3requency  atmospheric conditions  5ndoorBoutdoor 1ommon examples include 3ree space2 alfish,5kegami2 Jkumura,=ata2 Longley,ice2 Lee and oungMs models. The most commonly used model in urban environments is the Jkumura&=ata model as described below93or 8rban #reas93or mall and /edium&si>ed cities93or Large cities9where9  '!&! Mappig f Path Lsses t *ell +i,es 3or a path loss of 4'* d!2 based on the assumptions shown in the table below the following cell ranges can be attained with LTE. The cell range is shown for %%2 4-%%2 $4%% and $<%% /=> frequency bands.   -ssumptis   .kumura#/ata parameter0rba dr +uburba dr 2ural dr 2ural utdr fi3ed !ase station antenna height (m)+%<%-%-%/obile antenna height (m)4.<4.<4.<</obile antenna gain (d!i) %%.%%.%%.%<.% low fading standard deviation (d!)-.%-.%-.%-.%Location probability (D)<<<<1orrection factor (d!)%&<&4<&4<5ndoor loss (d!)$%4<%% low fading margin (d!)-.--.--.--.- *ell +i,e i m '!6! *mparis t .ther 2adi -ccess Techlgies
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