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mac protocol in wireless sensor networks

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Newbie level 1
Jan 29, 2014
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need help how to implement ,two level clustering in WSN to implement a cross layer mac protocol ,each level cluster head decide through the threshold high and threshold low,which is compared to RSS.First level CH will have RSS>thr-high,for the messages send by base station(BS-msgs).This first level CH sends CH-msg,whose RSS is compared to thr-high,if it is more than thr-high,then they become group memebers.IF the CH-msgs are received by nodes ,whose RSS is between thr-high and thr-low,they become 2nd level CH and choose the node with highest RSS as their parent to route info to BS.New CHs
may receive different CH-Msgs from previous-level CHs.
In this case, new CHs consider these messages in order to
construct multiple paths toward base station and sort these
paths based on certain criterions (such as link quality, endto-
end delay, bandwidth, or number of hops in the path).
Paths with good conditions, like high link quality, short endto-
end delay, enough bandwidth, or less number of hops,
are reserved for multimedia communication that requires
certain level of quality of service requirements. Other paths
will be used for other types of data that does not require strict
QoS requirements such as scalar data. If the RSSI is less than
Thr-Low, the message is considered as lost or ignored.two-level QoS-aware scheduling ,low-level scheduling within each cluster among the
GMs and high-level scheduling among the cluster heads in
order to increase the packet delivery ratio and throughput
for multimedia data.The low-level scheduling process is initiated by the CH by
sending a broadcast message asking each GM in the cluster
to send their requests informing about the type of data to
be transmitted, its amount, and its requirements (such as
playout deadline, BW, etc.). This broadcast message, Assign-
Msg, contains the control slot assignment (i.e., time slot to
each GM) in the cluster. The duration of the control slot is
enough to any node in the cluster to send its request message
(Req-Msg), and the time slot is unique for each GM to avoid
collisions. During the request phase, each GM sends a Req-
Msg to its CH at the allocated time slot informing about the
data to be sent (if available) and its QoS requirements.
Then based on the collected information from the
request phase, each CHgenerates a transmission schedule for
the active GMs and distributes it in the cluster. The resulting
schedule is sent to all GMs by broadcasting a scheduling
message, Sched-Msg, to inform each GM with the specified
time schedule for sending each type of data.

After receiving the schedule, each GMwill transmit its
data during the assigned time slots for each data type and the
CH sends, after receiving a certain number of data packets,
an Ack-Msg to the sender. When the data
transmission phase completes, a CH sends again the Assign-
Msg to its GMs to send their requests.
At higher level, each intermediate cluster head—in the
same manner done at low level—schedules the traffic toward
the sink from other cluster heads (its children) based on the
type of the data and its QoS requirements. THis is done in ns-2.

Please help with the coding part!!also about setting the threshold high and threshold low!!!!!!

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