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

4-June-07 P1901_PRO_016_r0
transmit to different nodes in the same transmission. Usually, this type of transmission will be only performed
for low service class traffic.
As it is described in the above time diagram, Inter PPDU Space (IPPDUSx) depends on the type of the next
frame to be transmitted. In the MAC Parameters Section, it is detailed the value of each Inter PPDU Space.
4.3.2 Data Frame
When a data frame is transmitted from a master to one of its slaves (the direction of the token is downstream),
the data token at the end of the data frame will indicate for how long the slave is allowed to transmit. This
length of time is known as the token validity, and is expressed as a number of symbols. The maximum length of
the data frame is limited by the validity.
Upon transmitting a data token, the node will enter reception mode.
When a CPE receives a data token, it may transmit a data frame for as long as the received data token validity
indicated. At the end of the frame, a data token is transmitted indicating the end of the transmission. At this
point, the master node will take over the channel again.
When a Time Division Repeater (TDR) receives a data token from its master node, it schedules the
transmissions between itself and the master node and also distributes new tokens among its slaves, for as long
as the received data token validity indicated.
The validity does not need to be fully used by the receiving node, and it will not be wasted: the validity only
sets the maximum length of time between the transmission of a token downstream and the return of this token,
and it does not reflect the actual length.
4.3.3 Silence Frame
A node transmits the silence frame when it does not want to transmit the token to another node at the end of the
frame or when no other kind of frames can be sent (or need to be sent). A silence frame may contain bursts with
payload data. Upon transmitting a silence token, the node shall transmit a new frame.
For instance, the silence frame may be used by a HE node that is alone in the network. In that situation it shall
send periodical access frames, and silence frames will cover the rest of the time. Another use is when the bursts
to be transmitted do not fit in one single MPDU. In such a case it is possible to transmit several consecutive
silence frames and a final data frame to pass the token to another node.
Upon reception of a silence token, no action needs to be done.
Submission page 96 UPA-OPERA