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

4-June-07 P1901_PRO_016_r0
4.3.4 Channel Estimation Frame
Periodically, every node has to send a channel estimation frame so that nodes communicating with that node
can estimate their channel and adjust their bit-loading table.
A channel estimation frame is composed by a token announce followed by a known pseudo-random sequence of
16 symbols. A channel estimation frame is not addressed to any specific node. Any node which receives a
Channel Estimation frame shall consider this frame if the transmitter MAC address included in the Token
Announce is part of a completed entry in the port solver table (see 9.1.4.1).
A channel estimation process may lead to the transmission of a bit-loading table calculated upon the reception
of a Channel Estimation Frame. The Adaptive Bit-Loading Protocol is used for the transfer of this bit-loading
table and its acknowledgement (see section 9.1.2). Every node is responsible for evaluating the appropriate time
to return the calculated bit-loading table. For instance, if there are major changes in the new calculated bitloading
table with respect to the previous one, the node can immediately return the new bit-loading table before
any other transmission is considered. If the new bit-loading table has undergone no changes, the node shall not
return any bit-loading table.
4.3.4.1 Transmission of channel estimation frames by TDRs and CPEs
TDRs and CPEs shall ask permission to their master to transmit a channel estimation frame. The channel
estimation frame sent by a TDR may be used by the master and the slaves of the TDR to estimate the channel
from the TDR. The channel estimation frame sent by a CPE may be used by the master of the CPE to estimate
the channel from the CPE. A TDR shall not transmit channel estimation frames within its validity period unless
the Allow channel estimation frame field received within the data token was set to 1 by its master, but can grant
rights to transmit channel estimation frames to its slaves.
As shown in Figure 31, the channel estimation process can be initiated either by the TDR or CPE (referred as
slaves) or its master.
Submission page 97 UPA-OPERA