Cross-layer adaptive design for the frame length of IEEE 802.11 networks

In this paper, we study the cross-layer (between MAC and PHY) design problem for IEEE 802.11 wireless networks. It is focused on the design of the optimal length of the frame body. The following results are obtained: 1) The optimal length of the frame body in logarithmic scale, expressed as log L
_f,opt
, can be coarsely approximated by a linear function of the signal-to-noise power ratio (SNR) E
_b
/N
₀
(in dB) and finely approximated by a second-order polynomial of E
_b
/N
₀
; 2) The coefficients of the aforementioned approximation functions depend only on the data transmission rate and other parameters specified in the protocol, and they do not depend on the access mechanisms; 3) The number of active nodes has little effect on L
_f,opt
, especially in the range of both low and high SNR; 4) The system throughput is sensitive to the length of the frame body L
_f
when the SNR is low, while it is insensitive to L
_f
in a considerably large neighborhood of L
_f,opt
when the SNR is high; and 5) Fragmentation can always increase the system throughput, but the increasing rate is conspicuous only in the low SNR regime.