8.3 Opportunistic Effective One-Hop Throughput (OEOT)
According to the analysis above, for a given next-hop neighbor set 
, we now introduce the local metric, Opportunistic Effective One-hop Throughput (OEOT) (in Equation (8.5)), to characterize the local behavior of GOR in terms of bit-meter advancement per second.
where 
, which is an ordered subset of 
with priority 
; 
; 
; 
; and
8.6 
which is the probability of none of the forwarding candidates in 
successfully receiving the packet in one physical transmission from the sender.
The physical meaning of the OEOT defined in Equation (8.5) is the expected bit advancement per second for a local GOR procedure when the sender S transmits the packet at rate Rj. Opportunistic Effective One-hop Throughput integrates the factors of packet advancement, relay reliability, and one-hop packet forwarding time. Now for multirate GOR, our goal is to select an Rj and the corresponding 
to locally maximize this metric. The intuitions to locally maximize the OEOT are as follows. 1. As the end-to-end achievable throughput is smaller than per-hop throughput on each link, to maximize the local OEOT is likely to increase the path throughput. 2. The path delay is the summation of per-hop delay, which is actually relative to the delay introduced by transmitting the packet and coordinating the candidates. As the per-hop delay factors (Ts and Tf(i)) are integrated in the denominators of OEOT, to maximize OEOT is also implicitly to decrease per-hop delay, which may further decrease the path delay. 3. As the transmission reliability of 
is also implicitly embedded in OEOT, maximizing OEOT also tends to improve the reliability. Reliability is a key factor affecting throughout and delay for the following reason. If a packet is transmitted on a low reliable link, several retransmissions are needed to make a successful packet forwarding at one hop. These retransmissions not only harm the throughput and delay performance of the flow that the packet belongs to but also introduce huge medium contentions to other flows, thus further decreasing the whole system performance. However, maximizing the one-hop reliability does not necessarily lead to better end-to-end throughput. Because reliable links likely have short hop distance, this short hop distance may result in taking many hops to deliver a packet from the source to the destination, which may also introduce a large delay or more medium contention to other flows. Our OEOT metric jointly takes into account the hop advancement, reliability and packet-forwarding time.