SYNC for MOTES

1
SYNC for MOTES

• Dream Lab, UC Irvine

2
Backgroup info. about Active Message

• Motes use Active Messages Layer to communicate
  each other.
• The advantage of the Active Message Layer is that
  it tranfers user data with hander name and a data
  payoff. When the message arrive at the
  destination, it trigger the hander to handle the
  data immediately, which can eliminates buffering
  difficulties, reduce network congestion and
  ensure perfomance.
• At one node, the Active Messages Layer can only
  handle a single message at a time. It is the
  appliation developer duty to cooperate
  transmissions in different modules to avoid
  coflicts.
• The Active Messages Layer cant receive a message
  while a transmission in progrogress.
• The packet size in TinyOS is fixed, 38
  bytes/packet. It is about 40ms from requesting
  to transmit the first bit to the reply of the
  tramission the last bit in one node. About
  78ms to finish a packet transmissioin between
  two nodes.
• (I am not sure about those data, I got them from
  the documents of TinyOS.)

3
Backgroup info. about Radio Comm.

• All the motes use the same radio channel for
  communication.
• It means that if two motes want to send a
  message by Radio at the same
• time, one will failed.
• There are a scheme CSMA (Carrier Sense Multiple
  Access) to solve communication conflict.
• Implement by diffierent kinds components in
  TinyOS, they are
• RADIO_BYTE, SEC_DEC_RADIO_BYTE,
  SEC_DEC_RAIO_BYTE_SIGNAL,
• In each RADIO_BYTE components

4
Backgroup info. about Radio Comm.(cont).

• It is said there is another scheme to solve radio
  comm. channel conflict
• It is implemented by MAC Layer.
• When a conflict happen, it just report the
  busy status to the appliction, and
• let application handle this situation, droping
  the message or re-transmitiing.
• (But I am not sure about it)
• If we use CSMA scheme, channel capacity is about
  25 packet/s.
• channel utilization is up to 70.
• So if we use the RADIO_BYTE components, we dont
  need consider conflicts in the application level.

5
Commucation Structure

• We suse a self-defined component MSG_TO_MFG to
  communicate between Motes by Radio Channel.
• We use another self-defined component
  GENERIC_BASE_UART to communicate between IPQ/PC
  by serial Ports

6
MSG_TO_RFM

• This module is changed from the modules
  INT_TO_RFM and RFM_TO_LEDS . This module can send
  by TOS_Msg out by accepting a TOS_COMMAND
  MSG_TO_RFM_OUTPUT(TOS_MsgPtr msg), using the
  Active Message Channel 4. And When a message
  coming from the Active Message Channel 4, it can
  also signal an event MSG_TO_RFM_MSG_ACCEPT(TOS_Ms
  gPtr msg) to the upper component. If you want to
  use another Active Message Channel, not 4, you
  can modify the file MSG_TO_RFM.desc.
• include modulesGENERIC_COMM
• This component is built on the shared componet
  GENERIC_COMM.
• GENERIC_COMM use a system radio byte level
  componet SED_DEC_RADIO_BYTE_SIGNAL for radio
  communication, so we dont need consider channel
  conflicts between motes.

7
GENERIC_COMM

• include modules AM_STANDARD
• UART_PACKET
• UART
• CRCPACKETOBJ_SIGNAL SEC_DED_RADIO_BYTE_S
  IGNAL
• RFM
• RANDOM_LFSR
• ADC

8
GENERIC_BASE_UART

• It is a generic base to communicate between PC
  and mote using UART. It accepted a command
  GENERIC_BASE_UART_OUTPUT(TOS_MsgPtr data) to send
  a data packet by serial port
• And when a data packet arrived from serial port,
  it signal a Event GENERIC_BASE_UART_DATA_READY(TOS
  _MsgPtr data)
• (I just write this commponent last night. And it
  have been tested until now.)
• include modules UART_PACKET
• UART

9
Other components needed

• One very important component we need is CLOCK.
• We use it the set the clock for the whole
  application.
• The another usefule components is LEDS, which is
  used for debugging.
• The sensor componets, MIC, SOUNDER, PHOTO, ,
  will be used in the data collection, which are
  not used in the sync. Module.
• Maybe sometimes we will use the sounder componet
  for debugging.

10
SYNC_MSG_TYPE

• define USER_DATA 0
• define ROUND_DELAY 1
• define ACK_ROUND_DELAY 2
• define RET_IPAQ_DELAY 3
• define SUB_MAX_DELAY 4
• define RET_SUB_DELAY 5
• define TMOSM_STARTUP_1 6
• define TMOSM_STARTUP_2 7
• define CLOCK_SYNC_1 8
• define CLOCK_SYNC_2 9
• define ERR_REPORT 10

11
IMPORTANT ASSUMPTIONs

• In order to ensure a channel Slience period to
  ensure sync-msg-communication, we define a global
  varaible SILIENCE_PERIOD for each mote node.
• In each mote node, except for the synchronization
  module, every other module should check
  SILENCE_PERIOD 0 before it send out a message.
• A fixed time(about 100ms to 200ms) before initial
  sync or re-synce time, we set the SILENCE_PERIOD
  1. So after about(50 t100ms), there will be no
  message be sent out in this mode mode.
• For the slience peroind is about 100 ms or more,
  we should take a longer re-sync period, maybe 5
  seconds. Or the clock synchronization will
  consume a lot of cpu time
• The data use in this design document should be
  tested and get a proper value later.

12
Initial Clock Synchronizatioin for iPAQ
START
Send ? back to master node with RET_IPAQ_DALAY
Take a timestamp T1
Send ROUD_DELAY msg to master mote
Sleep for t time
Wait for ACK_ROUND_DELAY msg from the master
node
Send TMOSM_STARTUP_1 to the master Node
Received ACK_ROUND_DELAY
TIME_OUT
NO
Sleep for ?ipaq
Yes
Yes
Take a time stamp T2, get ?temp T1 T2
abort
Set the local time to zero
Repeat above steps 3 times, get ?
average(?temp)
END
Wait for master mote to report its ?max for
comm. cost between motes
Received SUB_MAX_DELAY Msg?
TIME_OUT
NO
Yes
Yes
recieved ?max sub_max_delay ?ipaq ? ?max
abort
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Initial Clock Synchronizatioin for Master Node
START
Take a time stamp Tk, 2 Get ?rep the time
between node k receving ROUND_DELAY and sending
ACK_ROUND_DELAY
RECEIVE msg from iPAQ through GNERIC_BASE_UART
MSG ROUND_DELAY?
Yes
?temp Tk,2 Tk, 1 - ?rep Repeat this
round-trip several 3 times ?k
average(?temp) ?worstk max(?temp) ?max
max(?i)
Send ACK_ROUND_DELAY back to iPAQ cnt cnt 1
Send ACK_ROUND_DELAY back to iPAQ cnt cnt 1
cnt 3?
No
Repeat this round-trip 3 times
Global varibale SLIENCE_PERIOD 1 For each node
in the group, take a time stamp Tk, 1 .
Broadcast ROUND_DELAY msg with GROUP_ID
Send msg SUB_MAX_DELAY msg to iPAQ with the
value ?max Send msg RET_SUB_DELAY with
?k,?worstk.?max to the mote node K
Warit for ACK_ROUND_DELAY msg
Received ACK_ROUND_DELAY
TIME_OUT
NO
to be continued
Yes
14
Initial Clock Synchronizatioin for Master
Node(cont.)
Wait msg from iPAQ through GNERIC_BASE_UART
No
MSG RET_IPAQ_DELAY
Yes
Record the delay ?
No
MSG TMOSM_STARTUP_1
Broacast TMOSM_STARTUP_1
be idle for ?/2 then set clock as 0
be idle for t 50 ms time
Broadcast TMOSM_STARTUP_2
Be idle for ?max
Yes
Global varibale SLIENCE_PERIOD 0
END
15
Initial Clock Synchronizatioin for slave Node
START
No
MSG TMOSM_STARTUP_1
MSG TMOSM_STARTUP_2
No
Global varibale SLIENCE_PERIOD 1
Yes
Yes
RECEIVE msg from the radio channel
Abort
Set the local clock as 0
Group_id LOCAL_GROUP
Wait for TMOSM_STARUP_2
Yes
No
MSG TMOSM_STARTUP_2 Group_id LOCAL_GROUP
MSG ROUND_DELAY
Wait for time out ( ?max t ?worst/2)
Yes
No
No
Yes
Send ACK_ROUND_DELAY back to the MASTER
Yes
Yes
No
Set the local clock as t ?k/2
MSG RET_SUB_DELAY
No
be idle for ?max - ?k/2
Yes
Record ?k,?worstk.?max
SLIENCE_PERIOD 0
END
16
Re-synchronizatioin for iPAQ
Time for re-sync?
Send CLOCK_SYNC msg to master node with local
stamp
END
17
re-synchronizatioin for master mote
Note 1p is the maximum devation possibility
between master and slave notes. We havent got
the time until now. ? is the max length of period
, after which no message, except for the sync
msg, can be send out from this node. We assume
it 40 ms here. Note 2 For the slience peroind
is about 100 ms or more, we should take a longer
re-sync period, maybe 5 seconds. Or the clock
synchronization will consume a lot of cpu time.
Receive CLOCK_SYNC from iPAQ?
No
Yes
this_diff local_stamp iPAQ stamp diff
average(this_diff)
Time Tnr?
local stamp local stamp diff
Broacast CLOCK_SYNC_1
Time Tnr - p - ??
be idle for t time
Broadcast LOCAL_SYNC_2
Yes
SLIENCE_PERIOD 1
Be idle for ?max/2
Global varibale SLIENCE_PERIOD 0
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re-synchronizatioin for slave mote
Time Tnr - p - ??
No
Wait for time out ( 2 p ? t ?worst/2
?worst/2)
Msg CLOCK_SYNC_2?
No
No
Yes
SLIENCE_PERIOD 1
Go to the step
yes
Wati for the sync msgs
Wait for CLOCK_SYNC_2
Group_id LOCAL_GROUP?
No
Wait for time out ( t ?worst/2)
Msg CLOCK_SYNC_2 groupid LOCAL_GROUP
No
Yes
No
Msg CLOCK_SYNC_1
Yes
Yes
this_diff2 local_stamp master stamp diff2
average(this_diff) Local stamp local stamp -
diff2
Yes
this_diff1 local_stamp master stamp diff1
average(this_diff) Local stamp local stamp -
diff1
Report error(opt.)
Be idle for (?max - ?k) /2
SLIENCE_PERIOD 0