Smart Telecom Education Blog

PRACH Preamble Generation

The PRACH is time and frequency-multiplexed with PUSCH and PUCCH, PRACH time-frequency resources are semi-statically allocated within the PUSCH region, and repeat periodically. The PRACH occupies 6 PRBs in the frequency domain and in...

LTE Cell Search Procedure

there are Two relevant cell search procedures exist in LTE:
Initial synchronization;
and New cell identification.
In both scenarios, the synchronization procedure makes use of two specially designed physical signals which are broadcast in each cell: the Primary Synchronization Signal (PSS), and the Secondary Synchronization Signal (SSS).

LTE Accessibility Procedure

The LTE Accessibility is described in following Steps:
initially the UE is OFF.

Once the UE is powered ON.
the first step is Cell Search Procedure.
then Reception of System Information message from the Network.
followed by PLMN selection;
then the UE select a cell to camp on.

in this stage the UE can Access to the network by a Random Access and initial attach procedures.

LTE Downlink Power Calculation

The CRC power is indicated by the energy per resource element, and is determined by the Reference signal power parameter.
The Reference signal power parameter specifies the reference signal (RS) power output by a remote radio unit (RRU).
in PDSCH power setting, OFDM symbols in one timeslot can be classified into 2 types: type A symbols and type B symbols.
Type A: PDSCH resource elements where not in the same symbol as Reference signal resource element.
Type B: PDSCH resource elements in the same symbol as Reference signal resource element.

LTE PA Control

eNB supports power amplifier bias control by adjusting PA bias for low RF load without a specified carrier shutdown.

Two types of PA bias control mechanisms are supported: Predefined Time schedule based and Traffic load based.

Operator Benefits:
•PA bias control provides high power efficiency with low RF load.
•PA bias control saves about 6.7% of consumed DC power in 800MHz.

LTE Handover

Handover refers to a cell transition that occurs when a circuit-switched (CS) connection is in place (such as CS voice, CS data, or Dual Transfer Mode). Handovers can only be initiated by the network. During a handover, the network sends the mobile a Handover command, which provides information about the destination cell, including the traffic channel configuration.

The procedure for mobility from LTE to another RAT supports both handover and Cell Change Order (CCO).

The CCO procedure is applicable only for mobility to GERAN.

In case of handover (as opposed to CCO), the source eNodeB requests the target RAN node to prepare for the handover.

As part of the ‘handover preparation request’ the source eNodeB provides information about the applicable inter-RAT UE capabilities as well as information about the currently-established bearers. In response, the target RAN generates the ‘handover command’ and returns this to the source eNodeB.

LTE Cell reselection

Cell reselection is the process of changing the mobile’s serving cell (either in idle mode or while actively transmitting data).

Cell reselections can be initiated by the mobile or network. When the network initiates a cell reselection, it sends a Packet Cell Change Order (GPRS/EGPRS) or a Cell Change Order (W-CDMA/HSPA), which provides the parameters necessary for the mobile to find and synchronize to the destination cell.

If the mobile was actively transferring data at the time of the cell reselection, any subsequent allocation of traffic channel resources to continue the packet data transfer are handled by signaling between the mobile and destination cell, and does not involve the origination cell.

LTE Difference between CCO – Cell change Order and Redirection

CCO from LTE (only possible towards GSM) differs from the LTE->GSM redirection mainly such that with CCO if the UE can’t successfully camp and access the given target GSM cell, it has to return to LTE, whereas the redirection can have multiple target cells/frequencies and the UE can attempt to find service in any of them.

With Rel-9 redirection also the system information messages for the target GSM cell (or, in fact, up to maximum of 32 GSM cells) the performance can be equal (or even better in case the single target cell with CCO cannot be found or access fails) that the CCO with NACC (network assisted cell change, which means the system information for the target GSM cell is provided with the CCO).

In practise the above means that redirection typically would perform equally well and in many cases (esp. if the redirection or CCO is made blindly, i.e. without UE reporting GSM cells) better than CCO, and therefore it is typically used with CS fallback.

LTE Packet Loss Detection over S1

eNB counts and provide statistics about lost packets and out-of sequence packets occurred during delivery from SGW to eNB. This feature can be enabled only when eNB interworks with EPC.

Operator Benefits:
•Operator can decide the quality of backhaul network.

LTE Test of VSWR

The functionality of VSWR(Voltage Standing Wave Ratio) test is used to measure return loss in transmitting antenna of power amp unit.

Operator Benefits:
•This feature provides an efficient method for measuring return loss in transmitting antenna of power amp unit.