Page 250 - From GMS to LTE

236 From GSM to LTE-Advanced Pro and 5G

And finally, some symbols are reserved to acknowledge the proper reception of uplink
data blocks or to signal to the mobile device that a block was not received correctly. This
functionality is referred to as Hybrid Automatic Retransmission Request (HARQ) and
the corresponding channel is the Physical Hybrid Automatic Retransmission Request
Indicator Channel (PHICH).
In summary, it can be said that the PDSCH is transmitted in all RBs over the complete
system bandwidth. In each RB, however, some symbols are reserved for other purposes
such as the reference signals, the synchronization signals, the broadcast channel, the
control channel, the PCFICH and the HARQ indicator channel. The number of sym-
bols that are not available to the shared channel depends on the RB and its location in
the resource grid. For each signal and channel, a mathematical formula is given in 3GPP
TS 36.211 [11] so that the mobile device can calculate where it can find a particular kind
of information.

4.3.7 System Information Messages
As in GSM and UMTS, LTE uses System Information messages to convey information
that is required by all mobile devices that are currently in the cell. Unlike in previous sys-
tems, however, only the Master Information Block (MIB) is transported over the broad-
cast channel. All other system information is scheduled in the PDSCH and its presence is
announced on the PDCCH in a search space that has to be observed by all mobile devices.
Table 4.4 gives an overview of the different System Information Blocks (SIBs), their
content and example repetition periods, as described in 3GPP TS 36.331 [12]. The most
important system information is contained in the MIB and is repeated every 40 milli-
seconds. Cell‐related parameters are contained in SIB 1, which is repeated every 80

Table 4.4 System information blocks and content overview.

Message Content

MIB Most essential parameters required for initial access
SIB 1 Cell identity and access‐related parameters and scheduling information of System
Information messages containing the other SIBs
SIB 2 Common and shared channel configuration parameters
SIB 3 General parameters for intrafrequency cell reselection
SIB 4 Intrafrequency neighbor cell reselection information with information about
individual cells
SIB 5 Interfrequency neighbor cell reselection parameters
SIB 6 UMTS inter‐RAT cell reselection information to UMTS
SIB 7 GSM inter‐RAT cell reselection information to GSM
SIB 8 CDMA2000 inter‐RAT cell reselection information
SIB 9 If the cell is a femto cell, i.e. a small home eNode‐B, this SIB announces its name
SIB 10 Earthquake and tsunami warning system (ETWS) information
SIB 11 Secondary ETWS information
SIB 12 Commercial mobile alert system (CMAS) information