TelecomStudy18

TDMA   (Time Division Multiple Access) refers to a digital RF link where multiple phones share a single carrier frequency by taking turns. Each phone gets the channel exclusively for a certain time slice, then gives it up while all the other phones take their turn. TDMA is also used sometimes to refer specifically to the standard covered by IS-136, which is a source of confusion because   GSM  also uses a TDMA air interface, as does   IDEN , and neither of those systems are compatible with IS-136.

Rake receiver   is the digital section of a CDMA receiver which permits the phone (or cell) to separate out the relevant signal from all the other signals. The relevant signal will be encoded with a known   Walsh Code  and a known phase of the   Short code , and the rake receiver can do this because the Walsh codes are   orthogonal  and the Short code is orthogonal to itself at different offsets. The rake receiver is capable of receiving multiple signal sources and adding them together using multiple   fingers , each of which has the ability to use a separate phase of the short code and   long code  and a separate Walsh code if necessary. Different fingers might track multiple signals from the same cell (arriving at slightly different times due to   multipath ) or might track separate cells due to   soft handoff .

Chip in the context of CDMA is distinct from bit and refers to binary digits transmitted over the RF link. The chip rate in IS-95 is 1.2288 MHz (thus allowing adequate guard bands to permit the carriers to be spaced 1.25 MHz apart). Each bit is represented by many chips, and if a majority of the chips get through then the bit can be reconstructed properly. The number of chips representing each bit varies depending on the bit rate. When using an 8K Vocoder (such as EVRC) there are 128 chips for each bit. Chips as such don't contain data because both the sender and receiver know the spreading pattern used to create them from a bit, and as such are not directly subject to the laws of Information Theory. Though there are many phones simultaneously using a single frequency to transmit full chiprate, that means that the channel is not saturated unless the bitrate approaches the bandwidth of the carrier.

2G Handover Optimization Classification by Reason Timing advance (TA) Emergency HO Triggering condition _ The actual TA > TA HO Thrsh. Object cell selection _ The cell must be of the highest priority in the candidate cell sequence and meet the following restrictions. Restriction _ The service cell cannot be the object cell. _ HO is not allowed when TA Thresh. of the neighboring cell with the same BTS is smaller than that of the service cell. Bad Quality HO Triggering condition _ UL receiving quality >=UL receiving quality thrsh. of the service cell. _ OR DL receiving quality >=DL receiving quality thrsh. of the service cell. Object cell selection _ The cells must be of the highest priority in the candidate cell sequence and meet the following restrictions. Restriction _ Handover to the neighboring cell with the highest priority. If there is no neighboring cell, handover to the service cell, and the channel at different TR...

MIMO Systems can provide two types of gain: Spatial Multiplexing Gain and transmit Diversity Gain In Spatial Multiplexing Gain , maximum transmission rate  can be achieved by sending different  data streams at different antennas Whereas  in Diversity Gain, maximum quality(QOS) can be achieved  by sending same data streams to different antennas. There is a tradeoff between  these two gains as spatial diversity can be achieved under good radio conditions where as transmit diversity is done under poor radio conditions to achieve good quality. System designs are based on trying to achieve either goal or a little of both

Mobility Management Entity (MME) – MME is a controller at each node on the LTE access network. At UE in idle state (idlemode), MME is responsible for tracking and paging procedure which includes retransmission therein. – MME is responsible for selecting SGW (Serving SAE Gateway) which will be used during initial attach EU and the EU time to do intra-LTE handover. – Used for bearer control, a different viewR99/4 whichis still controlled by the gateway Serving SAE Gateway (SGW) -Set the path and forwards the data in the form of packets of each user-As an anchor / liaison between the UE and the eNBat the time of the inter handover-As a liaison link between the 3GPP LTE technology with the technology (in this case the 2G and 3G) Gateway Packet Data Network (PDN GW) -Provides for the UE 's relationship to the network packet-Provide a link relationship between LTE technology with technology non 3GPP (WiMAX) and 3GPP2 (CDMA 20001X and EVDO)

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 (Rece...