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The MME Function

NAS signalling;
NAS signalling security;
AS Security control;
Inter CN node signalling for mobility between 3GPP access networks;
Idle mode UE Reachability (including control and execution of paging retransmission);
Tracking Area list management (for UE in idle and active mode);
PDN GW and Serving GW selection;
MME selection for handovers with MME change;
SGSN selection for handovers to 2G or 3G 3GPP access networks;
Roaming;
Authentication;
Bearer management functions including dedicated bearer establishment;
Support for PWS (which includes ETWS and CMAS) message transmission.

In cellular networks, when a mobile moves from cell to cell and performs cell selection/reselection and handover, it has to measure the signal strength/quality of the neighbor cells. In LTE network, a UE measures two parameters on reference signal: RSRP (Reference Signal Received Power) and RSRQ (Reference Signal Received Quality).

RSRP is a RSSI type of measurement. It measures the average received power over the resource elements that carry cell-specific reference signals within certain frequency bandwidth. RSRP is applicable in both RRC_idle and RRC_connected modes, while RSRQ is only applicable in RRC_connected mode. In the procedure of cell selection and cell reselection in idle mode, RSRP is used.

RSRQ is a C/I type of measurement and it indicates the quality of the received reference signal. It is defined as (N*RSRP)/(E-UTRA Carrier RSSI), where N makes sure the nominator and denominator are measured over the same frequency bandwidth;

The carrier RSSI (Receive Strength Signal Indicator) measures the average total received power observed only in OFDM symbols containing reference symbols for antenna port 0 (i.e., OFDM symbol 0 & 4 in a slot) in the measurement bandwidth over N resource blocks. The total received power of the carrier RSSI includes the power from co-channel serving & non-serving cells, adjacent channel interference, thermal noise, etc.

The RSRQ measurement provides additional information when RSRP is not sufficient to make a reliable handover or cell reselection decision. In the procedure of handover, the LTE specification provides the flexibility of using RSRP, RSRQ, or both.

What are the possible causes for a Drop Call on a UMTS network?

What are the possible causes for a Drop Call on a UMTS network?

 Poor Coverage (DL / UL)

 Pilot Pollution / Pilot Spillover

 Missing Neighbor

 SC Collisions

 Delayed Handovers

 No resource availability (Congestion) for Hand in

 Loss of Synchronization

 Fast Fading

 Delayed IRAT Triggers

 Hardware Issues

 External Interference

What are the possible causes for an Access Failure in UMTS?

What are the possible causes for an Access Failure in UMTS?

· Missing Neighbors

· Poor Coverage

· Pilot Pollution / Spillover

· Poor Cell Reselection

· Core Network Issues

· Non – availability of resources. Admission Control denies

· Hardware Issues

Improper RACH Parameters
External Interference

What are the processing gains for CS and PS services

What are the processing gains for CS and PS services?

CS12.2: 25dB

PS-64: 18dB

PS-128: 15dB

PS-384: 10dB

HSDPA: 2dB

3G Basic Parameter

Basic Parameters of WCDMA

Frequency Band : 2100 MHz

1920-1980MHz (UL) &2110-2170 MHz (DL)

Duplex Space : 190 MHz

Channel bandwidth : 5 MHz

Coding Spacing : 200 KHz (RASTER)

UARFCN Range : 10562-10838 (Total ARFCN – 276)

Duplex mode : FDD and TDD

Downlink RF channel structure : Direct spread

Chip rate& Chips : 3.84 Mcps& It is pulse of spreading spectrum n

It’s in rectangular shape of +1 & -1

Frame length : 10 ms (38400 chips) = 15Slots, & 1slot = 2650chips

Superframe : A Superframe has a duration of 720ms and consists

Of 72 radio frames. The super frame boundaries are

Defined by the System Frame Number (SFN)

Spreading modulation : Balanced QPSK (downlink)

Dual-channel QPSK (uplink)

Complex spreading circuit

Data modulation : QPSK (downlink) & BPSK (uplink)

Channel coding : Convolution (Voice) and turbo (data) codes

Coherent detection : User dedicated time multiplexed pilot (DL and UL),

Common pilot in the downlink

Channel multiplexing in downlink : Data and control channels time multiplexed

Channel multiplexing in uplink : Control and pilot channel time multiplexed

I&Q multiplexing for data and control channel

Spreading factors : 4–256 (uplink), 4–512 (uplink)

Power control : Open and fast closed loop (1.6 kHz)

Power control period : 1500Hz

Power control step size : 0.5, 1, 1.5 and 2db

Power control range

Handover : Soft HO, softer HO, Inter frequency and IRAT HO

About Us

About Us Telecomstudy18

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Telecomstudy18 was launched on 14-Febuarary- 2013 with a dream to provide every possible guides and tutorials related to Fresher and Experience Telecom. The main goal of starting this blog is to build an active community of Telecom Engineer so that they can learn every aspect of technology GSM, WCDMA and LTE in a better way.

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This blog mainly focus on below categories:

GSM

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CDMA

LTE