" Wireless " Learning in Telecom

System Information (36.331 Rel 13 Mar 2016) SIB Description Comment MIB Downlink channel bandwidth, PHICH config SFN 1 PLMN, TAC, Cell Id, access restrictions, q-RxLevMin, frequency band, MFBI Scheduling of other SIBs 1 BR Bandwidth Reduced, limited channel bandwidth of 6 PRBs eMTC (enhanced Machine Type Communications) 2 Common radio resource config, access class barring, MBSFN config UL frequency and bandwidth 3 Cell re-selection common information 4 Cell re-selection information for intra-frequency neighbouring cells Black cell list 5 Cell re-selection information for inter-frequency neighbouring cells 6 Cell re-selection information for UTRA 7 Cell re-selection information for GERAN 8 Cell re-selection information for CDMA2000 9 Home eNodeB name 10 ETWS (Earthquake and Tsunami Warning System) Primary notification 11 ETWS Secondary notification 12 CMAS (Commercial Mobile Alert Service) notification 13 MBMS control information associated with one or more MBSFN...

S-GW The Serving Gateway (S-GW) provides user plane connectivity, the UE being on one side, and the Packet Data Network Gateway (P-GW) on the other side of the physical S-GW element. Depending on the network provider’s approach, these elements can be separate, or they can be combined physically as a single element. It should be noted that no control messaging goes between the UE and the S-GW, as the control plane is taken care of by the MME element. The S-GW element takes care of the following functionalities: . S-GW is the local anchor point for the inter-eNB handover procedure; . S-GW is also an anchor point for the inter-3GPP network mobility; . Lawful Interception (LI); . packet routing and forwarding; . S-GW handles packet buffering in the E-UTRAN idle mode; . S-GW handles the network initiated/triggered service request procedure; . packet marking at the transport level for both DL and UL; . Charging Data Record (CDR) collection, which can identify the UE, PDN an...

eNodeB The eNB element of LTE is responsible for radio transmission and reception with UE. eNB  provides the required functionality for the radio resource management (RRM), including  admission control, radio bearer control, scheduling of user data, and control signaling over  the air interface. In addition, eNB takes care of the ciphering and header compression over the  air interface. The clearest difference between UTRAN and E-UTRAN can be seen in the role of the base  station. The eNodeB of LTE now includes basically all the functionalities that were previously  concentrated on the RNC of the UTRANsystem. In addition, the traditional tasks of the NodeB  are still included in the new eNodeB ( eNB ) element. eNB works thus as the counterpart of the  UE in the radio interface but includes procedures for decision making related to the connections. This solution results in the term “flat architecture” of LTE, meaning that there are le...

Cell Search Procedure in LTE Thought of adding a small diagram, that explains the very important cell search procedure in LTE, which is the very first that any LTE UE will perform before initiating network entry procedure, For full explanation of cell search procedure Cell Search Procedure in LTE What is a cell search procedure? Who does this?  Why do we need this? How is this done? I will try to answer these questions related to the LTE cell search procedure. A cell search is nothing but a procedure that, any sniffer or a UE shall perform in order to get more details about the nearby eNodeB/cell. So this is the first step that a UE shall do, as soon as it is powered on. The cell search procedure, is the UE’s way of acquiring cell specific information and this, the UE has to perform once or several times based on the condition of the network. Basically the steps involved in cell search are as follows, after the UE is powered ON 1.  ...

What is  cyclic prefix or why do we need the CP in LTE or for that matter in any wireless/OFDM system? The answer lies in the name itself. Cyclic indicates that, the CP maintains the cyclic nature of something and prefix says it is added at the beginning. Basically, the CP is nothing but a portion of the signal itself, which is copied and added to the beginning of the signal. The below diagram should explain more about the same, Cyclic Prefix for LTE Why CP is added? Now to understand why CP is added, you should know the basics of FFT/IFFT or the significance of doing a FFT/IFFT over any signal. In LTE, for downlink, an IFFT is performed to realize the OFDM concept. Now, first place what does FFT does?What does IFFT does to a signal? If you take a FFT of a signal, you are basically taking the signal from time domain to frequency domain and for IFFT, it is the vice versa, i.e from frequency domain to time domain. Lets see what happens when we take a FFT of a...

Long Term Evolution (LTE) supports both FDD and TDD Duplex mode. The major difference in TDD and FDD is that in TDD system a single frequency is shared in time domain between Uplink  and Downlink where as in FDD separate frequencies are used for Uplink and Downlink transmission. A TDD frame structure is shown in below figure. 10 mili second radio frame consists of Downlink subframe, Uplink subframe and Special subframe. In TDD there are about 7 frame configurations, based on different DL/UL partition. Downlink/Uplink ratio can vary from 1/3 (Frame configuration = 0) to 8/1 (Frame configuration = 1). An operator can choose a specific TDD configuration depending on the service requirements Frame always starts with a Downlink subframe, used for advertising the frame descriptor information i.e. PCFICH and PDCCH. UE hence learns the frame structure in the subframe. 3rd frame is always used for Uplink transmission When switching from Downlink to Uplink, there is need for a Spe...