40 Questions
What is the term used in LTE to describe the base station?
ENODEB
What is the benefit of open interfaces in LTE?
Support of multivendor equipment interoperability
What is the purpose of self-optimization functionalities in LTE?
Efficient mechanisms for operation and maintenance
What is the term used to describe home base stations?
Femto-cells
What is the key feature of HSDPA that enabled fast packet scheduling over the radio interface?
Transmission of short packets having a duration of the same order of magnitude as the coherence time of the fast fading channel
What is the purpose of joint optimization of the physical layer configuration and the resource management in HSDPA?
To adapt to prevailing propagation conditions
What is the reduced packet duration in LTE compared to HSDPA?
1 ms, down from 2 ms in HSDPA
What is an example of a cross-layer technique used in LTE?
Adaptive scheduling in both the frequency and spatial dimensions
What percentage of VoIP packets are allowed to be discarded without affecting the user's satisfaction?
More than 2%
What is the broadcast performance requirement defined in terms of?
achievable system throughput (BPS) and spectral efficiency (BPS/Hz)
What is the maximum end-to-end delay allowed for VoIP packets in LTE systems?
200 ms
What percentage of the nominal coverage area is allowed to be in outage for broadcast services?
2%
What is the minimum percentage of satisfied users required to define the system capacity for VoIP?
95%
What is the broadcast spectral efficiency requirement set to?
1 BPS/Hz
How many satisfied VoIP sessions per MHz are required by the NGMN group of network operators?
60
What is the maximum speed of terminals that LTE is required to support?
Up to 350 km/h, or even up to 500 km/h
Why was the broadcast mode not available in Release 8?
due to higher prioritization of other service modes
What is the primary scenario for operation at high speeds in LTE systems?
Usage on high-speed trains
What is the minimum user plane latency calculated based on?
signalling analysis for the case of an unloaded system
What is the round-trip latency obtained by?
multiplying the one-way user plane latency by a factor of two
What is the maximum cell radius for which LTE is required to support handover without interruption?
Up to 5 km
What is the mode of operation required for high rate multimedia broadcast/multicast services in LTE systems?
Single frequency network mode
What is the IP-layer one-way data-packet latency required to be in optimal conditions?
as low as 5 ms
In addition to user plane latency, what other requirement was specified?
call setup delay was required to be significantly reduced
What was the main goal of designing LTE from the start?
To evolve the radio access technology with the assumption that all services would be packet-switched.
What is the term used to describe the evolution of the non-radio aspects of the complete system?
System Architecture Evolution (SAE)
What is the collective term for High-Speed Downlink and Uplink Enhancements (HSDPA and HSUPA)?
High-Speed Packet Access (HSPA)
What is the key feature of HSPA+ introduced in Release 7?
Higher-order modulation and multistream ‘MIMO’ operation
In which release of the 3GPP specification series was the first version of LTE made available?
Release 8
What is the main advantage of LTE compared to HSPA and HSPA+?
It was free to adopt radical new technology without the constraints of backward compatibility or a 5 MHz carrier bandwidth.
What are the two modes in which LTE can operate?
Frequency-Division Duplex (FDD) and Time-Division Duplex (TDD)
What is the name of the partnership organization similar to 3GPP that led a second evolution track?
3GPP2
What is the main feature of Release 9 that enhances the transmission modes?
The extension of the Release 8 beamforming mode to support two or more orthogonal spatial layers that can be transmitted to a single user or multiple users.
What are the new requirements defined in Release 9 for specific deployments?
New requirements for pico base stations and home base stations, in addition to improving support for closed subscriber groups (CSG).
What is the main goal of Release 10?
To fully satisfy the requirements set by ITU-R for the IMT-Advanced designation and even exceed them in several aspects.
What is one of the main features of Release 10 that fulfills the IMT-Advanced requirements?
Carrier aggregation, allowing the total transmission bandwidth to be increased up to 100 MHz.
What is the target peak spectral efficiency for uplink MIMO transmission in Release 10?
Greater than 7.5 bps/Hz and targeting up to 15 bps/Hz.
What is another feature of Release 10 that enhances LTE deployment?
Mechanisms to minimize the need for drive tests by supporting extended measurement reports from the terminals.
What type of transmission is introduced in Release 9?
Broadcast mode based on single frequency network type transmissions.
What is the improvement made in Release 9 for self-optimization of networks?
Enhanced self-optimization of networks.
Study Notes
LTE Overview
- LTE was designed to evolve radio access technology with the assumption that all services would be packet-switched, rather than circuit-switched.
- LTE is accompanied by an evolution of non-radio aspects of the complete system, under the term 'System Architecture Evolution' (SAE), which includes the Evolved Packet Core (EPC) network.
LTE Standardization
- The standardization of LTE and SAE has led to the original 'Release 99' specifications of UMTS being extended with high-speed downlink and uplink enhancements (HSDPA and HSUPA).
- HSPA has been further enhanced in Release 7 (becoming known as HSPA+) with higher-order modulation and, for the first time in a cellular communication system, multistream 'MIMO' operation.
LTE Releases
- The first version of LTE was made available in Release 8 of the 3GPP specification series.
- Release 8 introduced a new radio access technology that was able to benefit from the latest understanding and technology developments from HSPA and HSPA+.
- Release 9 introduced support for multiple 5 MHz carriers operating together in downlink and uplink.
- Release 10, also known as LTE-Advanced, develops LTE to satisfy the requirements set by ITU-R for the IMT-Advanced designation.
Performance Requirements
- LTE is required to support communication with terminals moving at speeds of up to 350 km/h, or even up to 500 km/h depending on the frequency band.
- The system capacity for VoIP can be defined as the number of users present per cell when more than 95% of the users are satisfied.
- The NGMN group of network operators expressed a preference for the ability to support 60 satisfied VoIP sessions per MHz.
Mobility and Cell Ranges
- LTE is required to support handover between cells without interruption, with imperceptible delay and packet loss for voice calls, and with reliable transmission for data services.
- The targets are to be achieved by the LTE system in typical cells of radius up to 5 km, while operation should continue to be possible for cell ranges of 100 km and more.
Broadcast Mode Performance
- The requirements for LTE included the integration of an efficient broadcast mode for high rate multimedia broadcast/multicast services (MBMS) such as mobile TV.
- The broadcast performance requirement was defined in terms of an achievable system throughput (bps) and spectral efficiency (bps/Hz) assuming a coverage of 98% of the nominal coverage area of the system.
User Plane Latency
- User plane latency is an important performance metric for real-time and interactive services.
- The minimum user plane latency can be calculated based on signalling analysis for the case of an unloaded system.
- The calculation should include typical HARQ retransmission rates (e.g., 0-30%).
Control Plane Latency and Capacity
- In addition to the user plane latency requirement, call setup delay was required to be significantly reduced.
- The control plane latency is defined as the average time between the first transmission of a data packet and the reception of a physical layer acknowledgement.
Technologies for LTE
- Packet switched radio interface applied across all layers of the protocol stack.
- Fast packet scheduling over the radio interface, using short packets having a duration of the same order of magnitude as the coherence time of the fast fading channel.
- Joint optimization of the physical layer configuration and the resource management carried out by the link layer protocols according to the prevailing propagation conditions.
LTE-Advanced
- The main Release 10 features that are directly related to fulfilment of the IMT-Advanced requirements are:
- Carrier aggregation, allowing the total transmission bandwidth to be increased up to 100 MHz.
- Uplink MIMO transmission for peak spectral efficiencies greater than 7.5 bps/Hz and targeting up to 15 bps/Hz.
- Downlink MIMO enhancements, targeting peak spectral efficiencies greater than 15 bps/Hz.
- Release 10 also provides some new features to enhance LTE deployment, such as:
- Support for relaying.
- Enhanced inter-cell interference coordination.
- Mechanisms to minimize the need for drive tests by supporting extended measurement reports from the terminals.
Learn about the design and evolution of LTE network architecture, including packet-switched technology and System Architecture Evolution (SAE).
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