Medium Access Control (MAC) and Physical Layer (PHY) - CISE

4-June-07 P1901_PRO_016_r0
4.3.4.2 Transmission of channel estimation frames by the HE
The process for the HE is different since it is the only node in the BPL cell that does not have a master.
The HE can send a Channel Estimation Frame as often as it deems necessary. At the end of the transmission of
a Channel Estimation frame by the HE, it is the HE which keeps the control of the medium.
The channel estimation frame sent by a HE may be used by the slaves of the HE to estimate the channel from
the HE. Each slave will have the opportunity to return the new calculated unicast bit-loading table (via the
ABLP protocol) as soon as it receives a data token from its master. However, as described above, the slave shall
not necessarily return the unicast bit-loading table as soon as it receives a data token following a Channel
Estimation frame.
4.3.5 Polling Frame
As described in 4.2.1, polling frames are used by the master to manage CPE state transitions from Idle to
Active or Idle to Unregistered.
Polling frames are frames terminated by a Polling Token. Polling Tokens are addressed to several CPE at the
same time via the Polling Destination Bank/Polling Destination Ports fields of the Polling Token (see 4.4.2.4,
Polling Token). A Polling Token is followed by a polling response sequence made of polling slots. The number
of polling slots included in this sequence corresponds to the number of bits set to 1 in the Polling Destination
Ports field of the polling token (max = 32). First bit set to 1 (going from the Least to the Most Significant bit)
corresponds to the first polling slot in the polling response sequence and so forth. Upon reception of a polling
token, a CPE which is addressed by this token shall assert a SOT in its corresponding polling slot if that answer
to the polling token is affirmative. It shall not respond if the answer to the polling token is negative.
Figure 32 shows a typical polling scheme in which three CPEs are polled. CPE 1 and CPE 3 assert a SOT in
their corresponding polling slots (affirmative response) while CPE 2 does not respond to the polling token
(negative response). Polling slots have duration equal to Size Poll Window. Two polling slots are separated by a
gap of Offset Poll Window. The last polling slot of the Polling Response Sequence is not followed by this gap:
the TX-RX Switch time shall be initiated immediately after the transmission of the last polling slot
Submission page 99 UPA-OPERA