Energy efficiency can be improved via making an efficient routing algo/protocol and also via effective MAC technique. For making you more clear I have attached a paper with this answer

I agree with the answer.

Thank you Sir.

Yes i agree effective routing protocol combined with proper MAC protocol is the best way to conserve energy in WSN 

Dear all,

Which parameters will help to measure and compare routing algorithms for better one in WSN or placement and routing in VLSI design ?

Thank you Ajit Negi.

The area of Research for better energy consumption or in other words increasing the network lifetime for WSN is very vast.  A huge research work has already been done and still one finds new techniques coming up. You can find lot of papers in the net relating to this topic. Efficient Cluster Head Selection, proper design o MAC protocol (MAC itself is a huge subject in WSN and so many varieties exists), even placement of the nodes (there exist papers on efficient placement of nodes), even use of Relay Nodes (placement of relay nodes) the number of relay nodes and their distribution depending on the distance of the base station are all interrelated for efficient energy consumption or prolonging network life time. 

It is quite an involved subject with lot of inter related factors. Hope it helps, All the best  for the research.

Thank you very much Sir.

There are two opposite force, the use of redundancy increase the delivery probability but increase the energy expenses, reducing the number of message could reduce the energy expenses but also reduce the probability that a message could be delivery because there are less opportunities that this could happen.

The use of explicit ack could help to reduce the number of message and also to increase the number of possible senders of a message.

A good routing algorithm that help to delivery message, using low energy or covering large distances could help, but the network topology could affect the effectivity of the routing strategies.

Some simulation have to be developed to evaluate the strategies that could be used in particular networks topologies.

Thank you Ricardo Gonza'lez.