Implementing supplemental error correction for XBEE?

i thinking of implementing supplementary error correction xbee connection.
the problem is, when xbee near end of range, "native" error correction insufficient , drops bytes @ random.
i need transfer 1k of data intact between computer , arduino. speed not critical.
i thinking of sending data index each byte , request resend of missing bytes. issue method is, require @ 16bit data index mean 3 bytes transferred each byte. if data connection reliable, not problem. since data connection isn't reliable, if byte dropped, how know if next byte received either first or second byte of data index or if data byte?
can suggest method handle this? dealing randomly dropped bytes no easy task!

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the issue method is, require @ 16bit data index mean 3 bytes transferred each byte.

if create packets contain start marker, packet number, 20 bytes, checksum , end marker, receiving end can find start , end markers, compute checksum, , determine if packet n received correctly. if not, don't acknowledge it. sender need send packet n again. if nth packet acknowledged, sender know not necessary send packet again.

you can change size of packet. larger packets have less overhead (the start , end markers, packet number, , checksum). tradeoff larger packets harder send/receive without lost/mangled bytes.

reliable power , proper xbee selection , configuration have lot packets getting through intact. haven't told xbees have, range data being transmitted, or how xbees configured or powered.

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