than what can be accomplished by relay-less wireless networks. The concept of network coding

(NC) that was originally conceived for wired networks can also be used for efficient

communication in wireless networks, owing to the ubiquitous nature of wireless transmissions.

Earlier, NC was applied only to the higher layers of protocol stack. Only recently researchers

have started exploring network coding at physical (PHY) layer in which, instead of bits, signals

are combined. In literature, PHY layer NC is also referred as symbol level network coding. In

this thesis, we considered performance evaluation of PHY layer NC scheme in OFDM based

relay assisted wireless networks. Specifically, we conducted simulation study by implementing a

canonical scenario consisting of three nodes, of which two of them constitute source and sink

nodes and one of them would act as a relay. The OFDM based PHY layer that we used is similar

to the one that is used in IEEE 802.11a standard. The relay node uses the popular decode and

forward joint modulation (DF-JM) technique, which as the name implies decode and forward

mechanism combined with joint encoding of data received from both the nodes. The

performance of DF-JM has been compared with the conventional decode and forward (DF)

technique. Our simulation results suggest that DF-JM based PHY layer NC outperforms the

conventional DF scheme across different scenarios of interest. We also considered the

performance of DF-JM scheme with relay selection and power allocation. Our simulation results

suggest that an equal power allocation among various relays gives better throughput values as

against that of the scheme where relay selection is combined with optimal power allocation. This

behaviour is contrary to what was observed in a related work where simple analog relays were

considered. The relatively better performance of the equal power allocation based DF-JM

scheme can be attributed largely to the less number of transmission slots that a DF-JM based

scheme would require, along with the diversity advantage of having all the relays transmit.