Cellular COMMUNICATIONS

CELLULAR
COMMUNICATIONS

LTE

Data Rate

Requirements And Targets to LTE


reduced delays, in terms of both connection establishment
and transmission latency;


increased user data rates;


increased cell
-
edge bit
-
rate, for uniformity of service
provision;


reduced cost per bit, implying improved spectral efficiency;


greater flexibility of spectrum usage, in both new and pre
-
existing bands;


simplified network architecture;


seamless mobility, including between different radio
-
access
technologies;


reasonable power consumption for the mobile terminal

Cell/User Throughput


Average cell throughput [bps/cell] and spectral
efficiency [bps/Hz/cell].


Average user throughput [bps/user] and spectral
efficiency [bps/Hz/user].


Cell
-
edge user throughput [bps/user] and spectral
efficiency [bps/Hz/user].


The metric used for this assessment is the 5
-
percentile
user throughput, obtained from the cumulative
distribution function of the user throughput.

Key Performance Requirements

Key Performance Requirements

Multiple Antenna Technology


Diversity gain.
Use of the space
-
diversity provided by
the multiple antennas to improve the robustness of the
transmission against multipath fading.


Array gain.
Concentration of energy in one or more
given directions via
precoding

or
beamforming
. This
also allows multiple users located in different directions
to be served simultaneously (so
-
called multi
-
user
MIMO).


Spatial multiplexing gain.
Transmission of multiple
signal streams to a single user on multiple spatial layers
created by combinations of the available antennas.

MIMO

Packet
-
Switched Radio Interface


Completely Packet Oriented Systems

LTE User Equipment

Network

The Access Network

Bearers


Minimum Guaranteed Bit Rate (GBR) bearers
which can be used for applications
such as VoIP.


have an associated GBR value for which dedicated
transmission resources are permanently allocated


Non
-
GBR bearers which do not guarantee any
particular bit rate.



web browsing or FTP transfer.


bandwidth resources are allocated permanently to the
bearer.

QoS

Handover

Lossless Handover

Logical and Physical Channel

Discontinuous Reception(DRX)


Reduce time in a reception mode in order to save
battery

Logical Channel Priority

OFDM

OFDM

Peak
-
To
-
Average Power Ratio



PAPR





Power amplifiers that are linear at wide range of
inputs are costly



Handset: Reduce PAPR

OFDMA

OFDMA/TDMA

Physical Layer

Channel Estimation



Transmission distort the signal and add noise





If transmitted signal is known, can estimate
distortion and apply inverse transformation on other
signals



Reference signal

Reference Signal

Two antennas

Link Adaptation

Channel Quality Indicator

Multiple Antenna

Multiple Antenna

Optimal Power Allocation

Multi
-
User Scheduling

Resource Scheduler

Partial Frequency Reuse

Partial Frequency Reuse

Handover

40

Evolution of the Radio Interface

EDGE EDGE+

W
-
CDMA HSPA HSPA+

2000

LTE




LTE
-
Advanced

40

2010

384Kb/s

1Mb/s

384Kb/s

42Mb/s

18Mb/s

100Mb/s

1000Mb/s

Standards availability