What is RB or Resource Block?

A Resource Block (RB) is a time- and frequency resource
that occupies 12 subcarriers (12x15 kHz = 180 kHz) and one slot (=0.5 ms).

RBs are allocated in pairs by the scheduler (then referred to as Scheduling Blocks).

Each OFDM symbol contains, if 64-QAM is used, 6 bits per subcarrier (15kHz). There are, if normal CP is used, 7 OFDM symbols per slot. This ends up with 6*7 = 42 bits per slot.

One slot is 0.5 ms which gives us 42/0.5ms = 84kbps per sub-carrier.
If the full bandwidth, 20MHz, is used, there are
20MHz/15kHz=1333 sub-carriers.

However, only 1200 of these are used for user data. This
corresponds to 100 resource blocks.

1200*84kbps = 100,8 Mbps.
With four MIMO layers, we should be able to achieve 403,2 Mbps
of raw data rate in the physical layer.
What about the user data rate? The data rates used for L1/L2
signaling, reference signals, PBCH, SCH, layer 3 signaling and protocol headers has to be subtracted from this figure.

Then we end up with approximately 320 Mbps of user data rate on RLC level??
In UL we have approximately the same calculation, except that the gain from MIMO cannot be included, since no SU-MIMO is used in UL. Hence, approximately 80-100 Mbps of theoretical bitrate should be possible to reach.

Self-Healing

Self-healing is a function that mitigates the faults automatically by triggering appropriate recovery
actions.

From the point of view of fault management, for each detected fault appropriate alarms are be generated by the faulty network entity, regardless of whether it is an automatically detected and automatically cleared fault, or an automatically detected and manually cleared fault.

The self-healing functionality monitors the alarms, and gathers necessary correlated information (e.g. measurements, testing result, etc.) and does deep analysis, and triggers appropriate recovery actions to solve the fault.

It also monitors the execution of the recovery actions and decides the next step accordingly. When self-healing iteration ends, the self-healing functionality generates
appropriate notifications to inform the Integration Reference Point (IRP) Manager of all the changes
performed.

This concludes the section on the new radio access network for LTE, and the following chapters cover the new Core Network entities required to support this new technology.

Self-Optimization

Based on the actual location of equipment, the optimization of the initial neighbour list is required,
(e.g. radio measurements of eNodeBs are required to solve the call drops or handover problems).

For this approach, RRC connections and their accompanying measurements can be used to gather
the needed information about their neighbours.

Known neighbours can be checked if they are really
appropriate concerning real RF conditions; new ones can be included based on information about detected cells in the UEs. Neighbour related parameters include:

Location of the neighbours (distance)

UE measurement reporting or eNodeB radio scanning for neighbours

Field strength information

Event measurements such as cell specific call drops or handover failures

Network Management System(EMS)/Element Management

System(NMS) configuration data

Planning tool data

Self-Configuration

Self-configuration is the process that is executed automatically after the physical installation of the
eNB.

An IP address is allocated to the new eNB.

The eNB connects to the OAM system for authentication, software download and configuration data download. The initial radio configuration and transport parameters configuration are completed, and the software is downloaded into the eNB.

The eNB connects to the OAM system for configuration data or normal network management.

The S1-links and X2-links are established and dependent nodes such as MMEs and eNBs are updated with new configuration data.

The inventory system in the OAM is informed that a new eNB is ready to perform the next required operation.

LTE MIMO

MIMO, (Multiple-input and Multiple-output), refers to the use of multiple antennas at both the
transmitter and receiver to improve communication performance. It is one of several forms of smart
antenna technology.

MIMO offers significant increases in data throughput and link range without additional bandwidth or
transmit power. This is achieved due to a higher spectral efficiency, (more bits per second per hertz
of bandwidth), and link reliability or diversity (reduced fading).

LTE supports Multi-Mode Adaptive MIMO for Downlink and Uplink, which accommodates both higher
data rate and wider coverage:

Single User MIMO for peak user data rate improvement.

Multi User MIMO for average data rate enhancement.

Collaborative/Network MIMO for cell edge user data rate boost.

Self Organizing Network - SON

SON in LTE

SON is a certain set of features defined as use cases in 3GPP and applied for LTE.

The feature sets, dependent on 3GPP releases (e.g. 8 or 9) are expected to benefit Operators by transforming possible network management operations into automatic executable software procedures, hence resulting in substantial savings in OPEX.

Automation is not a new concept for wireless networks, although with LTE this will prove to be more efficient, enabling the extensive use of automated processes. Thus, the appearance of SON algorithms represents a continuation of the natural evolution of wireless networks, where automated processes are simply extending their scope deeper
into the network.

SON features are distributed to eNB and EPC, and include Self Configuration, Self Optimization and
Self Healing features.

LTE stands for Long Term Evolution.LTE is a standard for 4th generation (4G) mobile broadband which is aimed to be the successor to the 3G technologies GSM/UMTS.

LTE is already implemented in many countries but still in the early stage.

LTE is also considered the competitor to WiMAX.

LTE promises to provide theoretical peak download rates of up 100Mbps (rates with varies based on environment etc) and peak upload rates of up to 50Mbps.

LTE is a better technology than wimax becauste LTE will make people free from the burden of having to find a WiFi hotspot (Wimax) when they are on the road.

As long as you have an LTE modem, LTE subscribers can connect to the internet anywhere in the service provider's coverage area!

Download Ericsson LTE Perspective in PDF

The LTE standard includes:

Peak download rates of 326.4 Mbit/s for 4x4 antennas, 172.8 Mbit/s for 2x2 antennas for every 20 MHz of spectrum.

Peak upload rates of 86.4 Mbit/s for every 20 MHz of spectrum.

5 different terminal classes ranging from a voice centric class up to a high end terminal that supports the peak data rates. All terminals will be able to process 20 MHz bandwidth.

At least 200 active users in every 5 MHz cell.

(i.e., 200 active data clients)

Sub-5ms latency for small IP packets.

Increased spectrum flexibility, with spectrum

slices as small as 1 .5 MHz .and as large as 20 MHz. W-CDMA requires 5 MHz slices, leading to some problems with roll-outs in countries where the 5 MHz spectrum is
already allocated to 2 - 2.5G legacy GSM and cdmaOne. The 5 MHz chunks also limit
the amount of bandwidth per handset.

■ Optimal cell size of 5 km, 30 km sizes with reasonable performance, and up to 100 km cell sizes supported with acceptable performance.

■ Co-existence with legacy standards (users can transparently start a call or transfer of data in an area using an LTE standard, and should coverage be unavailable, continue the operation without any action on their part
using GSM/GPRS or W-C DMA-based UMTS or even 3GPP2 networks such as cdmaOne
orCDMA2000) .

■ Support for MBSFN (Multicast Broadcast Single Frequency Network). This feature can
deliver services such as MBMS using the LTE infrastructure, and is a competitor to DVB-h.

A large amount of the work is aimed at simplifying the architecture of the system, as it evolves from the existing hybrid (packet and circuit switching) network,
to an all-IP flat architecture system.

Advantages of LONG TERM EVOLUTION or LTE

LTE advantages include high throughput, low
latency, plug and play from day one, FDD and TDD
in the same platform, superior end-user experience
and simple architecture resulting in low operating
expenditures (OPEX). LTE will also support
seamless connection to existing networks, such as
GSM, CDMA and WCDMA. However LTE requires a
completely new RAN and core network deployment
and is not backward compatible with existing UMTS
systems.

LTE targets requirements of next generation
networks including downlink peak rates of at least
1 0OMbit/s, uplink rates of 50 Mbit/s and RAN (Radio
Access Network) round-trip times of less than 10ms.
LTE supports flexible carrier bandwidths, from
1 .4MHz up to 20MHz as well as both FDD
(Frequency Division Duplex) and TDD (Time Division
Duplex).

LTE further aspires to improve considerably spectral
efficiency, lowering costs, improving services,
making use of new spectrum and refarmed spectrum
opportunities, and better integration with other open
standards. The resulting architecture is referred to as
EPS (Evolved Packet System) and comprises the
E-UTRAN (Evolved UTRAN) on the access side and
EPC (Evolved Packet Core) via the System
Architecture Evolution concept (SAE), on the core
network side.

RRC States were restricted to RRC_Idle and RRC_Connected States. They are depicted below, in conjunction with the possible legacy UTRAN RRC States (extract of TR 25.813):

In adddition, the Next Generation Mobile Networks (NGMN) initiative, led by seven network operators (*) provided a set of recommendations for the creation of networks suitable for the competitive delivery of mobile broadband services. The NGMN goal is "to provide a coherent vision for technology evolution beyond 3G for the competitive delivery of broadband wireless services".


The NGMN long-term objective is to "establish clear performance targets, fundamental recommendations and deployment scenarios for a future wide area mobile broadband network". In a white paper (March 2006), they provided relative priorities of key system characteristics, System recommendations and detailed requirements.



Emphase was also on the IPR side, where the goal was "to adapt the existing IPR regime to provide a better predictability of the IPR licenses (...) to ensure Fair, Reasonable And Non-Discriminatory (FRAND) IPR costs" (NGMN White paper, March 2006).

All RAN WGs participated in the study, with collaboration from SA WG2 in the key area of the network architecture. The first part of the study resulted in agreement on the requirements for the Evolved UTRAN.



As a result, Technical Report (TR) 25.913 contains detailed requirements for the following criteria:

Peak data rate

* Instantaneous downlink peak data rate of 100 Mb/s within a 20 MHz downlink spectrum allocation (5 bps/Hz)
* Instantaneous uplink peak data rate of 50 Mb/s (2.5 bps/Hz) within a 20MHz uplink spectrum allocation)

Control-plane latency

* Transition time of less than 100 ms from a camped state, such as Release 6 Idle Mode, to an active state such as Release 6 CELL_DCH
* Transition time of less than 50 ms between a dormant state such as Release 6 CELL_PCH and an active state such as Release 6 CELL_DCH

Control-plane capacity

* At least 200 users per cell should be supported in the active state for spectrum allocations up to 5 MHz

User-plane latency

* Less than 5 ms in unload condition (ie single user with single data stream) for small IP packet

User throughput

* Downlink: average user throughput per MHz, 3 to 4 times Release 6 HSDPA
* Uplink: average user throughput per MHz, 2 to 3 times Release 6 Enhanced Uplink

Spectrum efficiency

* Downlink: In a loaded network, target for spectrum efficiency (bits/sec/Hz/site), 3 to 4 times Release 6 HSDPA )
* Uplink: In a loaded network, target for spectrum efficiency (bits/sec/Hz/site), 2 to 3 times Release 6 Enhanced Uplink

Mobility

* E-UTRAN should be optimized for low mobile speed from 0 to 15 km/h
* Higher mobile speed between 15 and 120 km/h should be supported with high performance
* Mobility across the cellular network shall be maintained at speeds from 120 km/h to 350 km/h (or even up to 500 km/h depending on the frequency band)

Coverage

* Throughput, spectrum efficiency and mobility targets above should be met for 5 km cells, and with a slight degradation for 30 km cells. Cells range up to 100 km should not be precluded.

Further Enhanced Multimedia Broadcast Multicast Service (MBMS)

* While reducing terminal complexity: same modulation, coding, multiple access approaches and UE bandwidth than for unicast operation.
* Provision of simultaneous dedicated voice and MBMS services to the user.
* Available for paired and unpaired spectrum arrangements.

Spectrum flexibility

* E-UTRA shall operate in spectrum allocations of different sizes, including 1.25 MHz, 1.6 MHz, 2.5 MHz, 5 MHz, 10 MHz, 15 MHz and 20 MHz in both the uplink and downlink. Operation in paired and unpaired spectrum shall be supported
* The system shall be able to support content delivery over an aggregation of resources including Radio Band Resources (as well as power, adaptive scheduling, etc) in the same and different bands, in both uplink and downlink and in both adjacent and non-adjacent channel arrangements. A “Radio Band Resource” is defined as all spectrum available to an operator

Co-existence and Inter-working with 3GPP Radio Access Technology (RAT)

* Co-existence in the same geographical area and co-location with GERAN/UTRAN on adjacent channels.
* E-UTRAN terminals supporting also UTRAN and/or GERAN operation should be able to support measurement of, and handover from and to, both 3GPP UTRAN and 3GPP GERAN.
* The interruption time during a handover of real-time services between E-UTRAN and UTRAN (or GERAN) should be less than 300 msec.

Architecture and migration

* Single E-UTRAN architecture
* The E-UTRAN architecture shall be packet based, although provision should be made to support systems supporting real-time and conversational class traffic
* E-UTRAN architecture shall minimize the presence of "single points of failure"
* E-UTRAN architecture shall support an end-to-end QoS
* Backhaul communication protocols should be optimised

Radio Resource Management requirements

* Enhanced support for end to end QoS
* Efficient support for transmission of higher layers
* Support of load sharing and policy management across different Radio Access Technologies

Complexity

* Minimize the number of options
* No redundant mandatory features

As a consequence the WGs have dedicated normal meeting time to the Evolution activity, as well as separate ad hoc meetings.

RAN WG1 assessed six possible radio interface schemes (evaluations of these technologies against the requirements for the physical layer are collected in TR 25.814).

The wide set of options initially identified by the early LTE work was narrowed down, in December 2005, to a working assumption that the downlink would use Orthogonal Frequency Division Multiplexing (OFDM) and the uplink would use Single Carrier – Frequency Division Multiple Access (SC-FDMA). Although opinions were divided, it was eventually concluded that inter-Node-B macro-diversity would not be employed. More information is given in the report of RAN#30.

Supported downlink data-modulation schemes are QPSK, 16QAM, and 64QAM. The possible uplink data-modulation schemes are (pi/2-shift) BPSK, QPSK, 8PSK and 16QAM.

The use of Multiple Input Multiple Output (MIMO) scheme was agreed, with possibly up to four antennas at the mobile side, and four antennas at the Cell site.

Re-using the expertise from the UTRAN, the same channel coding type than for UTRAN was agreed (turbo codes).

RAN WG2 has also held a first meeting to approach the radio interface protocols of the Evolved UTRAN (link). The initial assumptions were:

* Simplification of the protocol architecture and the actual protocols
* No dedicated channels, and hence a simplified MAC layer (without MAC-d entity)

* Avoiding similar functions between Radio and Core network.

A Transmission Time Interval (TTI) of 1ms was agreed (to reduce signalling overhead and improve efficiency).