In FDM, the sub-carriers are separated in the frequency domain to avoid interference between the sub-channels It results in a loss of spectrum efficiency because the frequency guard band can not be used to send data. The OFDM allows one to remove the frequency guard band. Benefit: There are more sub-carriers, so more symbols … Read more
All MS transmit on same frequency but with different PN codes to create different logical channels. Some channels marked for Access are used for signaling and control. While Walsh Codes identifies different channels, PN codes are used to identify Cells (by 15 bit code) and MS’s (by 42 bit codes). As each MS receives a … Read more
The use of multiple antenna technology allows the exploitation of the spatial domain as another new dimension. This becomes essential in the quest for higher spectral efficiencies With the use of multiple antennas the theoretically-achievable spectral efficiency scales linearly with the minimum of the number of transmit and receive antennas employed, at least in suitable … Read more
Adopting a multicarrier approach for multiple access in LTE was the first major design choice. The choice of multiple-access schemes was made in December 2005, with OFDMA being selected for the downlink, and SC-FDMA for the uplink. Both of these schemes open up the frequency domain as a new dimension of flexibility in the system, … Read more
If some knowledge of the downlink channels of the different transmit antennas, (more specifically some knowledge of the relative channel phases) is available at the transmitter side, multiple transmit antennas can be used to shape the overall antenna beam in the direction of a target receiver. In general, such beamforming can increase the signal-strength at … Read more
Functions of the cdma2000 Signaling Services Layer The Signaling Services Layer processes all messages exchanged between the mobile and the base station. These messages control such things as call setup and tear down, hand offs, feature activation, system configuration, registration and authentication. In the mobile, the Signaling Services Layer is also responsible for maintaining the … Read more
A parallel 3GPP R8 project to LTE and SAE is the Evolved High Speed Packet Access, eHSPA, project (also referred to as HSPA+). The proposed eHSPA features represent a logical evolution from today’s HSDPA and HSUPA systems. Roughly speaking, the eHSPA project focuses on three areas: • Optimising HSPA for real-time packet data services, like … Read more
Figure shows the network architecture of the Evolved Packet Core (EPC). The EPC consists of three main nodes: the Mobility Management Entity (MME), the Serving Gateway (SGW) and the Packet Data Network Gateway (PGW). The MME may be co-located with the SGW, and the SGW may be co-located with the PGW. Hence, the standard allows … Read more
The uppermost evolution track shown in Figure is that developed in the 3rd Generation Partnership Project (3GPP), which is currently the dominant standards development group for mobile radio systems and is described in more detail below. Within the 3GPP evolution track, three multiple access technologies are evident: the ‘Second Generation’ GSM/GPRS/EDGE family1 was based on … Read more
When the radio wave propagates in the air, the electric field direction changes regularly. If the electric field direction of radio wave is vertical to the ground, the radio wave is vertical polarization wave If the electric field direction of radio wave is parallel with the ground, the radiowave is horizontal polarization wave Propagation of … Read more