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Table 1 Notations and meanings

From: An SNR-based admission control scheme in WiFi-based vehicular networks

Notation Meaning
S Length of space for each vehicle
L i Transmission range of an AP when the specific transmission rate r i is used
q Vehicle arrival rate that counts the number of vehicles passing a fixed roadside observation point per unit time
v Vehicle speed
k Vehicle density
v f Speed when the vehicle is alone on the road
k jam Traffic jam density when traffic flow comes to a halt
λ Mean vehicle arrival rate
T i Sojourn time in the coverage of 2L i
p N Steady state probability with N vehicles in the coverage of an AP
C i Maximum number of vehicles in the coverage of an AP
I Elapsed time since the light turned red
M Number of remaining vehicles after the last green light signal
E Number of outgoing vehicles during the green light signal
T(N) Overall transmission time of a single node when N nodes exist
t tr MAC protocol data unit (MPDU) transmission time
t ack MAC acknowledgement transmission time
t pr Physical layer convergence protocol (PLCP) preamble and header transmission time
t ov Constant overhead that includes DIFS = 50 μ s, SIFS = 10 μ s, tack , and tpr
tcont(N) Channel contention time when N nodes exist
G i Group of nodes with the i th highest transmission rate r i
N i Number of nodes included in G i
t ov r i Constant overhead time of a node in G i
T i Overall transmission time of a node in G i
Tjam(N) Average time spent by collisions when N nodes exist
b Number of groups
P C (N) Conditional collision probability when N nodes exist
CW min Minimum contention widow size
X l Expected throughput of a super group (1, ...,l)
SNR i SNR threshold to be a member of G i