LTE has been designed as a completely packet-oriented multi service system, without the reliance on circuit-switched connection-oriented protocols prevalent in its predecessors. In LTE, this philosophy is applied across all the layers of the protocol stack. The route towards fast packet scheduling over the radio interface was already opened by HSDPA, which allowed the transmission … Read more
Subscriber Identity Module (SIM) The SIM as mentioned previously is a “smart card” which plugs into the ME and contains information about the MS subscriber hence the name Subscriber Identity Module. The SIM contains several pieces of information: International Mobile Subscriber Identity (IMSI)This number identifies the MS subscriber. It is only transmitted over the air … Read more
When the handset first powers up, it does an exhaustive search for the best pilot. No windows are used in this process. On the paging channel, the handset learns the window sizes SRCH_WIN_A, N, R and uses them when looking for neighbors both in idle mode and during calls. When a strong neighbor is requested … Read more
Advantages of CDMA Handoff It is “soft”, meaning that communication is not interrupted by the handoff. This is sometimes called “make before break.” This means fewer dropped calls for users and higher customer satisfaction for operators. The handoff is not abrupt, but rather it is a prolonged call state during which there is communication via … Read more
The mobile station continuously searches for Pilots to detect the presence of other CDMA signals that have the same carrier frequency and measures the strength (received Ec/Nt) of the pilots. When the mobile station detects a Pilot of sufficient strength that is not associated with the serving cell/sector, it sends a message to the serving … Read more
A data-modulation scheme defines how the data bits are mixed with the carrier signal, which is always a sine wave. There are three basic ways to modulate a carrier signal in a digital sense: amplitude shift keying (ASK), frequency shift keying (FSK), and phase shift keying (PSK). In ASK the amplitude of the carrier signal … Read more
Location Area Identity (LAI) PAGING message is broadcast within a local area, the size of which depends on traffic, paging bearer capability, signaling flow , etc. Format: MCC+MNC+LAC MCC: Mobile Country Code, 3 digits. MNC: Mobile Network Code, 2 digits. LAC: Location Area Code, a 2-byte-long hexadecimal BCD code. 0000 cannot be used with FFFE. … Read more
Transmit Diversity MISO = Multiple Input Single Output Principle More complex than SISO. 2 or more transmitters and one receiver. MISO is more commonly referred to as transmit diversity. The same data is sent on both transmitting antennas but coded in such a way that the receiver can identify each transmitter. Benefits Transmit diversity increases … Read more
Reverse Access Channel used by MS Initiate Communication or Respond to Paging Channel. A reverse channel is first spread with WALSH to 307.2Kbps and then becomes 1.2288Mcps after long code modulation. The long code here not only spreads spectrum, but implements the function of channelization. “Data burst randomizer” means discarding repeated chips during the transmission … Read more
OVSF Code (Orthogonal Variable Spreading Factor) is used as channelization code Orthogonal codes are easily generated by starting with a seed of 1, repeating the 1 horizontally and vertically, and then complementing the -1 diagonally. This process is to be continued with the newly generated block until the desired codes with the proper length are … Read more