LTE:
Tries to satisfy the necessities that appeared when data usage started to grow.
Only supports packet-switching.
Belongs to the third generation of mobile networks because it doesn’t achieve IMT-Advanced requirements.
Belongs to the fourth generation of mobile networks because it does achieve IMT-Advanced requirements.
Some of the fourth generation requirements are:
Minimum bit rates of 100 Mbps in the downlink and 50 Mbps in the uplink.
Support for broadcast and multi-cast.
Scalable bandwidth from 0 to 20 MHz.
High VoIP capacity.
LTE uses different modulations for its links:
OFDMA is used for the uplink and SC-FDMA for the downlink.
OFDMA is used for the uplink and WCDMA for the downlink.
WCDMA is used for the uplink and OFDMA for the downlink.
OFDMA is used for the downlink and SC-FDMA for the uplink.
The cyclic prefix:
Can be just normal.
May be normal or extended.
Lasts 5.2 us the first time and 4.7 us all other times in the normal case, and lasts 16.7 us in the extended case.
Lasts 5.2 us the first time and 4.7 us all other times in the extended case, and lasts 16.7 us in the normal case.
The frame:
Has a duration of 10 ms and is subdivided into ten 1 ms subframes, each of which is split into two 0.5 ms slots.
Has a duration of 10 ms and is subdivided into five 2 ms subframes, each of which is split into two 0.5 ms slots.
Has a duration of 1 ms and is subdivided into ten 0.1 ms subframes, each of which is split into four 0.025 ms slots.
Has a duration of 10 ms and is subdivided into ten 1 ms subframes, each of which is split into four 0.25 ms slots.
In LTE:
The smallest unit of resource is the Resource Block, which consists of one subcarrier for a duration of one OFDM symbol.
The smallest unit of resource is the Resource Element, which consists of one subcarrier for a duration of one OFDM symbol.
Each unit of 12 subcarriers (with a subcarrier spacing of 15 kHz) for a duration of one slot is termed a Resource Element.
Each unit of 12 subcarriers (with a subcarrier spacing of 15 kHz) for a duration of one slot is termed a Resource Block.
Some of the downlink’s physical channels and signals are:
Physical Hybrid ARQ Indicator Channel (PHICH).
Physical Broadcast Channel (PBCH).
SRS (Sounding Reference Signal).
PRACH (Physical Random Access CHannel).
About E-UTRAN:
Is formed by eNodeBs inter-connected with each other by means of interfaces called X2 and to the EPC by means of the S1 interface.
X2 interfaces are used to avoid data loss during handovers, to perform load balancing and to perform cancel interference.
Is formed by diverse entities, such as MME, S-GW or P-GW.
ENodeBs are responsible for managing and allocating radio resources, controlling mobility, positioning, IP headers compression among others.
The MME:
Serves as a local mobility anchor for the handover between eNodeBs and between 3GPP (GPRS, UMTS, etc.).
It is the control node that processes the signaling between the UE and the CN, on which the Non-Access Stratum (NAS) protocols are applied.
Is responsible for IP address allocation to UEs, and for activities related to quality of service and flow management.
Defines the rules for charging and policy control.
About innovations:
LTE-A is considered as belonging to the fourth generation.
LTE-B provides physical layer improvements and higher energy efficiency.
The architecture of LTE-B consists of elements such as VLR, AUC, or MSC among others.
LTE-A makes use of relays to improve coverage.
