error in LEACH
 

I get this error in Leach.err

can't read "env(RCA_LIBRARY)": no such variable
while executing
"source $env(RCA_LIBRARY)/ns-ranode.tcl"
(file "mit/uAMPS/sims/uamps.tcl" line 9)
invoked from within
"source.orig mit/uAMPS/sims/uamps.tcl"
("uplevel" body line 1)
invoked from within
"uplevel source.orig[list $fileName]"
invoked from within
"if [$instance_ is_http_url $fileName] {
set buffer [$instance_ read_url $fileName]
uplevel eval $buffer
} else {
uplevel source.orig[list $fileName]
..."
(procedure "source" line 8)
invoked from within
"source mit/uAMPS/sims/uamps.tcl"
(file "tcl/mobility/leach.tcl" line 18)
invoked from within
"source.orig tcl/mobility/leach.tcl"
("uplevel" body line 1)
invoked from within
"uplevel source.orig[list $fileName]"
invoked from within
"if [$instance_ is_http_url $fileName] {
set buffer [$instance_ read_url $fileName]
uplevel eval $buffer
} else {
uplevel source.orig[list $fileName]
..."
(procedure "source" line 8)
invoked from within
"source tcl/mobility/$opt(rp).tcl"
(file "tcl/ex/wireless.tcl" line 187)

CAN ANYONE JUST HELP ME CLEARING THIS OUT..PLZ