[SensorNetArch] suggested edits

[Jerry Zhao]

only two minor suggestions so far for section 1-3:

1. one point of the paper is that contrast to IP for internet, SP for
sensornet need to be pushed a bit lower than the network layer. This is
never mentioned  in the intro section. On the other hand, this is a
short position paper and it is tricky even enough to validate why sensor
network architecture, I also feel OK that we do not show the whole hand
in the intro. I am sure we will claim this in the abstract anyway. 

2.  Section 3, paragraph 3: It is a bit awkward for me to read the long
sentence: 
"To support the network protocols found in the sensornet literature, the
underlying mechanisms over which a caller of the send operation should
be able to exert control include generation of link level
acknowledgments, performance of initial and collision-avoidance
backoffs, post-media arbitration timestamping, degree of FEC,
retransmission and power management (cf. \cite{bmac})." 

It seems that sentence is not complete? Maybe reworded as: 

"To support the network protocols found in the sensornet literature,
caller of a send operation should be able to exert control over the
underlying SP mechanisms, including generation of link level
acknowledgments, performance of initial and collision-avoidance
backoffs, post-media arbitration timestamping, degree of FEC,
retransmission and power management (cf. \cite{bmac})."


Thanks, 
Jerry