Tài liệu Data Segmentation

The division of the transmission resources in the time domain usually causes segmentation
of larger data units (e.g. IP packets) into smaller data units. This is necessary because the
data has to fit into data segments carried by the time slots provided by a TDMA scheme. At
the same time, the data segmentation ensures a finer granularity of the network capacity
and a simpler realization of QoS guarantees. Thus, if network resources are divided
into smaller accessible portions, it is easier to manage the network resources and share
them between various telecommunications services, ensuring realization of their particular
QoS requirements. Furthermore, the data segmentation also ensures a higher efficiency
in the case of disturbances. So, if a disturbance occurs, a data segment or a number of
segments is damaged, and only damaged segments should be retransmitted (e.g. by an
ARQ mechanism,). Accordingly, a smaller portion of the network capacity is used for the
retransmission, which improves the network utilization.
On the other hand, a data segment consists in a general case of two parts; a header
field and a payload field. The payload is used for storage of the user information to be
transmitted over the network, and the header field consists of information needed for
the control functions of the MAC and other network layers (e.g. control of data order,
addressing, etc.). Therefore, the segmentation causes an additional overhead and there
is a need for optimization of the data segment size, which depends on the disturbance
characteristics in network