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LTE and LTE advanced
EPL657
1
IMT and IMT-Advanced Technologies• LTE, LTE Advanced and Wireless MAN-Advanced, are
designed to enable high speed Internet/Broadband at anytime, anywhere, with higher level of user-level customization.
• As per ITU for IMT-Advanced technologies, the targeted peak data rates are up to 100 Mbit/s for high mobility and up to 1 Gbit/s for low mobility scenario. Scalable bandwidths up to at least 40 MHz should be provided
• key technologies:– Orthogonal Frequency Division Multiplex (OFDMA)– Multiple Input Multiple Output (MIMO) and – System Architecture Evolution (SAE)
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MIMO Multiple Input Multiple Output
• Uses multiple transmitter and receiver antennas, whichallow independent channels to be created in space.
• Various Approaches for MIMO:– Space diversity:- to improve the communication reliability by
decreasing the sensitivity to fading by picking up multiplecopies of the same signal at different locations in space.
– Beamforming:- antenna elements are used to adjust thestrength of the transmitted and received signals, based ontheir direction for focusing of energy.
– Spatial Multiplexing:- Increased capacity, reliability,coverage, reduction in power requirement by introducingadditional spatial channels that are exploited by using space-time coding
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OFDMA Orthogonal Frequency Division Multiple Access
• Based on the idea of dividing a given high-bit-rate data stream into several parallel lower bit-rate streams and modulating each stream onseparate carrier – often called sub-carriers ortones.
• Multi-carrier modulation scheme minimizeinter-symbol interference (ISI) by making thesymbol time large enough so that the channel-induced delays are an insignificant (<10%)fraction of the symbol duration.
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OFDMA Orthogonal Frequency Division Multiple Access
• OFDM is a spectrally efficient version of multi-carriermodulation where sub-carriers are selected such thatthey are all orthogonal to one another over the symbolduration, thereby avoiding the need to have nonoverlapping sub-carrier channels to eliminate inter-carrier interference .
• Guard intervals are used between OFDM symbols. Bymaking the guard intervals larger than the expectedmulti-path delay spread, Inter Symbol Interference(ISI) can be completely eliminated
5http://en.wikipedia.org/wiki/Orthogonal_frequency-division_multiplexing
OFDMA Orthogonal Frequency Division Multiple Access
• OFDMA can be used as a multi-access scheme, wherethe available sub-carriers may be divided into severalgroups of sub-carriers called sub-channels. Differentsub channels may be allocated to different users as amultiple access mechanism. This type of multi accessscheme is called OFDMA.
• OFDMA is essentially a hybrid of FDMA and TDMA.Users are dynamically assigned sub-carriers (FDMA)in different time slots (TDMA).
• OFDMA is a flexible multiple access technique thatcan accommodate many users with widely varyingapplications, data rates and QoS requirements.
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LTE Long Term Evolution
• Capabilities:-– Scalable bandwidth up to 20 MHz, covering 1.4, 3, 5, 10, 15,
and 20 MHz
– Up/Downlink peak data rates up to 86.4/326 Mbps with 20MHz bandwidth
– Operation in both TDD and FDD modes
– Reduced latency, up to 10 ms round-trip times between userequipment and the base station, and up to less than 100 mstransition times from inactive to active
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LTE Specifications and speed
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Parameter Details Peak downlink speed with 64QAM in Mbps 100 (SISO), 172 (2x2 MIMO), 326 (4x4 MIMO) Peak uplink speeds(Mbps) 50 (QPSK), 57 (16QAM), 86 (64QAM)
Data type All packet switched data (voice and data). No circuit switched.
Channel bandwidth (MHz) 1.4, 3, 5, 10, 15, 20 Duplex schemes FDD and TDD
Mobility 0 - 15 km/h (optimised), 15 - 120 km/h (high performance)
Latency Idle to active less than 100ms Small packets ~10 ms
Spectral efficiency Downlink: 3 - 4 times Rel 6 HSDPA Uplink: 2 -3 x Rel 6 HSUPA
Access schemes OFDMA (Downlink) SC-FDMA (Uplink)
Modulation types supported QPSK, 16QAM, 64QAM (Uplink and downlink)
LTE Advanced: Key features• Features:-
– Compatibility of services– Enhanced peak data rates to support advanced
services and applications (100 Mbit/s for high and 1 Gbit/s for low mobility).
– Spectrum efficiency: 3 times greater than LTE.– Peak spectrum efficiency: downlink – 30
bps/Hz; uplink – 6.75 bps/Hz.– Spectrum use: ability to support scalable
bandwidth use and spectrum aggregation when non-contiguous spectrum needs to be used.
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Release 4
Release 5
Release 6
1.28Mcps TDD
HSDPA, IMS
HSUPA, MBMS, IMS+
Release 7 HSPA+ (MIMO, HOM etc.)
Release 8 LTE, SAEITU-R M.1457
IMT-2000 Recommendations
Release 9
Release 10 LTE-Advanced
1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011
GSM/GPRS/EDGE enhancements
Release 99 W-CDMA
Small LTE/SAE enhancements
3GPP specification releases
LTE-Advanced 주요표준동향및요소기술
Comparison chart
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WCDMA (UMTS)
HDPA HSPA+ LTE LTE Advanced
Max downlink speed( bps) 384 k 14 M 28 M 300M 1G
Max uplink speed (bps) 128 k 5.7 M 11 M 75 M 500 M
Latency round trip time(approx)
150 ms 100 ms 50ms (max)
~10 ms less than 5 ms
3GPP releases Rel 99/4 Rel 5 / 6 Rel 7 Rel 8 Rel 10
Access methodology CDMA CDMA CDMA OFDMA SC-FDMA
OFDMA / SC-FDMA
• The LTE UE (User Equipment) categories or UEclasses are needed:– to ensure that the base station (eNodeB) can communicate
correctly with the user equipment.– So the base station is able to determine the performance of
the UE and communicate with it accordingly.
• Five different LTE UE categories defined with a widerange in the supported parameters and performancee.g. LTE category 1 does not support MIMO, but LTEUE category five supports 4x4 MIMO.
The Second meeting of SATRC Working Group on Spectrum 12-13 December 2011 Colombo, Sri Lanka 12
LTE User Equipment categories
LTE User Equipment categories
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LTE UE category data rates
Category 1 2 3 4 5
Downlink 10 50 100 150 300
Uplink 5 25 50 50 75
LTE UE category modulation formats supported
Category 1 2 3 4 5
Downlink QPSK, 16QAM, 64QAM
Uplink QPSK, 16QAMQPSK,16QAM,64QAM
Requirements for LTE-Advanced [1]
General requirement
LTE-Advanced is an evolution of LTE LTE-Advanced shall meet or exceed IMT-Advanced requirements within the ITU-R time plan Extended LTE-Advanced targets are adopted
LTE-Advanced 주요표준동향및요소기술
Requirements for LTE-Advanced [2]
LTE-Advanced 주요표준동향및요소기술
Comparison between IMT-Advanced and LTE-Advanced LTE-Advanced should at least fulfill or exceed IMT-
Advanced requirements
ITU Requirement 3GPP Requirement
Peak data rates 1Gbps in DL 500Mbps in UL
Bandwidth 40MHz (scalable BW) Up to 100MHz
User plane latency 10ms Improved compared to LTE
Control plane latency 100ms Active Active dormant(<10ms) Camped Active (<50ms)
Peak spectrum efficiency 15bps/Hz in DL 6.75bps/Hz in UL
30bps/Hz in DL 15bps/Hz in UL
Average spectrum efficiency Set for four scenarios and several antenna configurations See next slide for case 1 requirement
Cell edge spectrum effciency
VoIP capacity Up to200 UEs per 5MHz Improved compared to LTE
Requirements for LTE-Advanced [3]
LTE-Advanced 주요표준동향및요소기술
System performance requirements for IMT-Advanced
ITU system performance requirement
Enviromnet Indoor Micro‐cell Base coverage Urban
Rural/ High speed
Spectrum Efficiency
DL (4x2 MIMO)
3 2.6 2.2 1.1
UL (2x4 MIMO)
2.25 1.8 1.4 0.7
Cell EdgeSpectrumEfficiency
DL (4x2 MIMO)
0.1 0.075 0.06 0.04
UL (2x4 MIMO)
0.07 0.05 0.03 0.015
Requirements for LTE-Advanced [4] System Performance Requirements from TR 36.913
Peak Spectral Efficiency:DL 30bits/Hz (8x8 MIMO), UL 15bps/Hz (4x4 MIMO)
Seem to be easily achievable by means of extended utilization of # of antennas
Average Spectral Efficiency (SE) and Edge Spectral Efficiency for LTE Case-1System performances of LTE Rel-8 are about 30% ~ 70% lower than 3GPP target
What would be key enabling technologies to fill up the gap between two?
LTE-Advanced 주요표준동향및요소기술
Antena
config
LTECell Avg. SE
[bps/Hz/cell] (3GPP R1‐072580)
LTE‐ADVCell Avg. SE
[bps/Hz/cell] (3GPP TR36.913)
LTECell Edge SE
[bps/Hz/user] (3GPP R1‐072580)
LTE‐ADVCell Edge SE
[bps/Hz/user] (3GPP TR36.913)
UL 1x2 0.735 1.2 0.024 0.04
2x4 ‐ 2.0 ‐ 0.07
DL 2x2 1.69 2.4 0.05 0.07
4x2 1.87 2.6 0.06 0.09
4x4 2.67 3.7 0.08 0.12
Performance issues
• Peak data rate• Delay• Average sector throughput• Quality of Service (QoS)
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Perfromance• Peak data rates are often perceived as actual data rates a
subscriber will experience on a wireless network; this is however far from the reality.
• Peak data rates do not take into account factors like trafficload, fading, attenuation loss and the signal to noise ratiothat have an impact on the end subscriber data rate in afixed line environment, and an even greater impact in wireless networks.
• In wireless, additional factors such as the surrounding environment and atmospheric conditions also affect theachievable data rates. This results in a real world data ratethat is well below the theoretical peak data rate obtained in laboratory environments
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Performance• Many different ways to measure performance of
wireless technologies which take into account various conditions and scenarios. These include: – peak throughput, – average sector throughput, – cell edge throughput and – subscriber data rate
• To accurately predict realistic live LTE network capacity and achievable subscriber experience, operators need to understand the different performance measurements.
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Perfromance• Radio transmission is broadcast via a radio base station, this
equipment transmits the radio signals which are received by end user equipment (UE).
• Radio signal quality affected by several factors, such as the signal path loss; this is essentially the reduction in power density of the signal as it moves through the environment in which it is traveling.
• Other factors that affect the signal strength include free space loss which affects the subscriber’s signal as he moves away from the transmitting base station. The signal also suffers if its path is obstructed by a factor known as diffraction or if the signal is reflected and reaches the receiver via a number of different paths. This results in performance degradation known as multipath.
• In effect, the less path loss and susceptibility to interference, the better the signal strength a UE experiences. The better the quality of signal received, the better the performance and throughput achieved by the subscriber.
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Performance
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effects of signal path loss suffered by radio signals due to factors such as free space loss, multipath, buildings and vegetation, diffraction and the general atmosphere.
Performance issues• new adaptive modulation schemes and techniques
compensate for environmental factors, delivering more capacity and better range in an inherently noisy environment full of obstacles
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• One example is adaptive modulationprovides tradeoff between delivered bit rate and robustness of digital encoding, in order to balance throughput with error resilience.
In areas where signal strength is good, modulation switches to a higher bit rate with less robust encoding, while in areas where signal strength is poor or there are a lot of multi-path reflections, the modulation switches to a lower bit rate with more robust encoding to minimize errors.
Thus highest throughput occurs closer to tower
Performance issues
• Several factors impact the practical throughput in RF systems– additional overhead added by
adaptive modulation and error correction coding affect actual data rate experienced by a user, significantly lowering the user experienced data rate compared to the physical layer peak data rates measured in the lab.
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Performance issues• LTE technology is spectrally efficient hence gets
more bits per second over a fixed bandwidth than previous technologies and as a result, if you take into account a reasonable error rate coding, you reach a peak data rate that is more realistic for commercial deployment.
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Antenna Technology Channel Bandwidth and Data Rates
TYPE QTY 5MHz 10MHz 20MHz
MIMO 2x2 43 86 173
MIMO 4x4 82 163 326
Antenna Technology Channel Bandwidth and Data Rates
TYPE QTY 5MHz 10MHz 20MHz
MIMO 2x2 29 59 117
MIMO 4x4 55 113 226
Table 1a – LTE Peak Data Rates (Mbps) – no error rate coding
Table 1b – LTE Peak Data Rates (Mbps) –5/6 error rate coding
Performance issues
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Figure 5 – LTE Sector Throughput compares the average sector throughput capacity of various cellular radio technologies
LTE provides a significant improvement in Average Sector Throughput capacity across all channel bandwidths when compared to other 3GGP technologies by leveraging 2X2 MIMO and OFDM.
Performance issues
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Comparing LTE and HSPA+ performance across entire cell areaNote Conditions - LTE is based on 2.6GHz and UMTS is 2.1GHz showing realistic performance in the field
Performance issues• With LTE’s all IP, flat architecture, the initial data
packet connection is much faster, typically 50 ms, and then between 12-15 ms roundtrip latency afterwards.
• The low latency of LTE, combined with its high average sector throughput, makes it an ideal platform for demanding services like video, gaming, and VoIP.
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Performance issues• QoS classes ensure network can prioritize certain types of
packet for immediate and secured delivery; can provide differentiated types of service, with potential for offering creative new billing models while offering subscribers a guaranteed level of service.
• The class of QoS and Guaranteed Bit Rate (GBR) are significantly dependent on the level of latency (delays in packet transmission), jitter (variation in latency), and dropped packets that occur in the network.
• Without a QoS implementation on a loaded network, subscribers will experience choppy videos, echo and delays in voice resulting in poor audio quality on voice calls.
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Performance issues• Realistic average subscriber data rate
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UMTS LTE a technology view
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SLIDES ADAPTED FROM: UMTS LTELawrence HarteAlthos Publishingweb: www.Althos.com
Also see http://www.ece.gatech.edu/research/labs/bwn/surveys/ltea.pdf
LTE• standard for wireless data communications technology
and an evolution of the GSM/UMTS standards. • goal of LTE was to increase the capacity and speed of
wireless data networks using new DSP (digital signal processing) techniques and modulations that were developed around the turn of the millennium.
• A further goal was the redesign and simplification of the network architecture to an IP-based system with significantly reduced transfer latency compared to the 3G architecture.
• The LTE wireless interface is incompatible with 2G and 3G networks, so that it must be operated on a separate wireless spectrum.
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LTE• Universal mobile telecommunications
system - UMTS - Long Term Evolution -LTE– set of projected improvements to the 3rd generation
wireless systems - 3G, including – 100 Mbps+ data transmission (peak) rates, – reduced transmission delays (reduced latency), – increased system capacity and – shorter transmission latency times. – Commonly referred to as nearly 4G (even though it is
not a ‘true’ 4G technology for which true 4G is sometimes used for LTE Advanced)
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LTE SYSTEM• allows cellular carriers to offer a very efficient
(more subscribers per cell site) mix of multimedia services (voice, data, and video) for existing (mobile telephone) and new (Internet and television) customers.
• designed to permit advanced and reliable services including media streaming and large file transfers. – new services offer potential of higher average revenue per user
than existing 1st and 2nd generation mobile customers. – for existing mobile carriers that upgrade to LTE, marketing is
geared towards acquiring new data-only and mobile television customers.
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LTE specification• provides downlink peak rates of 300 Mbit/s, uplink peak rates of 75
Mbit/s and QoS provisions permitting a transfer latency of less than 5 ms in the radio access network.
• can manage fast-moving mobiles and supports multi-cast and broadcast streams.
• supports scalable carrier bandwidths, from 1.4 MHz to 20 MHz and supports both frequency division duplexing (FDD) and time-division duplexing (TDD).
• IP-based network architecture, called the Evolved Packet Core (EPC) and designed to replace the GPRS Core Network, supports seamless handovers for both voice and data to cell towers with older network technology such as GSM, UMTS and CDMA2000.
• simpler architecture results in lower operating costs (for example, each E-UTRA cell will support up to four times the data and voice capacity supported by HSPA)
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LTE• natural evolution of 3GPP GSM and UMTS WCDMA networks.
Since LTE provides services above the original 3rd generation (3G) requirements, but does not provide service levels for 4th generation (4G) requirements, it is sometimes called “Beyond 3G”.
• key attributes include a variable bandwidth (1.4 MHz up to 20 MHz) OFDM radio channel, the co-existence of multiple physical channels on the same frequency using channel codes, many logical (transport) channels, separate signaling channels, multiple service QoS types, multi-system operation, and other advanced operational features.
• Each wide (20 MHz) LTE RF channel can have more than 800 simultaneous communication channels. Some of the channels are used for control purposes, while others are used for voice (audio) and user data transmission.
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Recall: what is UMTS
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Mobile Communication System - Universal Mobile Telephone System - UMTS - is a wide area broadband wireless communications system that uses digital radio transmission to provide voice, data, and multimedia communication services.
Recall: What is UMTS?• A UMTS system coordinates communication between mobile devices (user
equipment), radio access radio sites (UTRAN), and uses a packet switching core network to connect UMTS devices to other devices or networks.
• Digital Media Formats - LTE is designed to transfer digital information in packet data format.
• Functional Sections - The LTE system is composed of three key sections:
– - User Equipment (UE) - A device that converts media to and from UMTS LTE radio signals.- UMTS Terrestrial Radio Access Network (UTRAN) - Assemblies that convert digital signals to radio signals that can be sent to mobile devices and receive radio signals that can be converted back to their digital form. - UTRAN is divided into enhanced node B base stations - eNB - parts that are located at the cell site and radio network controllers - RNC - that coordinate the distribution and reception of communication connections.- Core Network (CN) - The CN performs the interconnection between the base station parts and other networks such as the public switched telephone network - PSTN - and public Internet. The core network is composed of high speed packet data switches, databases, and administrative control services.
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LTE key features
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LTE key featuresLTE key features include high speed data transmission, low latency packet data transmission, flexible frequency allocation, self-configuration capability, all IP core network, and multibeam transmission.UMTS LTE data transmission rates can reach up to 100 Mbps for the downlink and up to 50 Mbps for the uplink.UMTS LTE packet data transmission is significantly low allowing for low latency applications (such as VoIP Internet Telephony).The UMTS LTE system can use a mix of radio channel frequency bandwidths and duplex transmission types allowing for UMTS to be deployed in small amounts of spectrum.The UMTS LTE system was designed for automatic configuration and radio transmission optimization reducing the operational complexity and cost.The UMTS LTE switching system (the core network) only uses IP connections between network components simplifying design and deployment. This standardizes the equipment and service requirements simplifying design complexity and lowering support costs.UMTS LTE can use multibeam transmission to increase distance, reliability, and provide more capacity.
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LTE: UMTS evolution
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LTE: UMTS evolution• UMTS LTE natural evolution of 3GPP GSM and UMTS WCDMA
networks. Because LTE provides services above the original 3rd
generation (3G) requirements but does not provide service levels for 4th generation (4G) requirements, it is sometimes called “Beyond 3G.”
• 0G - Mobile Telephone before cellular• 1G - Analog Cellular• 2G - Digital Cellular• 2.5G - High Speed Packet Data• 3G UMTS WCDMA - Multimedia• 3G UMTS LTE - Ultra Broadband Packet Data• (cellular) mobile communication evolved from single user per radio
channel (analog) to shared high-speed multimedia broadband channels. One key benefit of evolution is ability of a mobile carrier to provide more services in same amount of radio channel bandwidth. If carrier upgrades system radio equipment and adds customers with new mobile technologies (and eventually gets rid of the old), they lower service costs (or make more money). 42
LTE services
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LTE services• GSM voice service started as a full rate voice service that allowed 8
users per GSM radio channel. The original design allowed for the use of a half rate voice service (lower quality audio) to incrase the number of simultaneous GSM voice users to 16 per radio channel.
• GSM Data services started as low speed circuit switched data (9.6 kbps). The GSM system evolved to allow the combination of multiple circuit switched data connections to provide high speed circuit switched data services - HSCSD.
• GSM short messaging service - SMS messaging service for extremely short text messages (140 characters). SMS evolved into executable messages that allow for advanced two-way messaging features.
• GSM Multicast - GSM has capabilities of one to many type servicessuch as group call (dispatch type services) and voice broadcast (such as traffic alerts).
• GSM Packet Data - GPRS - The GSM system evolved allowing users to dynamically share packet data resources on one or more GSM channels for services such as Internet browsing.
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LTE devices
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LTE devices• UMTS LTE devices range from fixed adapters (e.g. home network
termination units) to network termination adapters that allow a mix of device types to connecto the UMTS LTE system. – UMTS LTE mobile telephones may include the capability to use UMTS LTE
radio channels and other types of radio signals (such as WCDMA, GSM, CDMA2000, and WiMAX).
– Multimode UMTS LTE mobile device allows service providers to gradually migrate users in their systems to areas that can provide UMTS LTE radio services.
• Mobile Telephones - Portable devices that can be used for voice communication.
• PCMCIA Air Cards - Cards that can slide into computers to provide data services.
• Embedded Radio Modules - Radio assemblies that can be built-in or installed in devices such as laptop computers, video cameras, or digital signage displays.
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LTE devices• External Radio Modems - Assemblies that can be connected to other
devices through USB, Ethernet, or other connection types to provide data services.
• Network Termination Units (NTUs) - A receiver assembly that can produce one or more outputs that can be connected to devices such as home telephones, computers, or television sets.
• Media Players - Portable devices that can receive and display multimedia.
• Location Devices - Devices that can capture and/or display position location information.
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LTE Radio
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LTE RadioLTE radio is the transmission of control and user information in packet data format through a wide RF channel which usually operate on frequency bands around the world ranging from 800 MHz to 2 GHz.
LTE was designed as a Multimode system which allows mobile devices to transfer between the LTE system and other types of systems such as GSM, WCDMA, or even CDMA2000.
Multiple Types of Modulation - The LTE system can transmit using different types of modulation - QPSK and QAM- to allow the system to increase the data transmission rate when low distortion radio conditions exist.
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LTE RadioMultiple Input Multiple Output (MIMO) - UMTS systems can use multiple transmission paths to increase the distance and reliability of radio transmission.Variable Channel Bandwidth - The RF channel bandwidth can be dynamically assigned to allow the UMTS flexibility for bandwidth assignment (narrow channels) and increasing data transmission rates when bandwidth is available.FDD or TDD Operation - UMTS system can used paired frequencies- FDD - or shared single frequencies - TDD to allow UMTS systems to operate in a mix of frequency bands.
The LTE system can use multiple types of modulation. The lowest level modulation type (and most robust) is Quadrature Phase Shift Keying - QPSK modulation. When radio conditions permit, 16-QAM can be used to increase transmission capacity. If radio conditions permit, 64-QAM may be used. Complexity and cost of 64-QAM, mobile devices may not include a 64-QAM transmission option.
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LTE modulation types
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figure shows that amplitude and phase modulation - QAM - can be combined to form an efficient modulation system.
In this example, one digital signal changes the phase and another digital signal changes the amplitude. This allows a much higher data transfer rate as compared to a single modulation type.
LTE MIMO radio transmission
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A multiple input multiple output (MIMO) transmission system transmits signals over multiple paths to a receiver where they are combined to produce a higher quality signal. example shows that a single beam transmission signal can have deep signal fade levels. When two or more beams are used, the signal fades are minimized, resulting in a more even (error free) signal.
LTE system can use multiple input multiple output - MIMO - radio transmission to provide increased transmission reliability and higher data transmission rates.
LTE dynamic bandwidth configuration
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LTE system can dynamically change its transmission bandwidth up to 20 MHz by adding or removing sub-carrier channels. Figure shows how LTE system can dynamically assign bandwidth through the allocation of sub-carriers. This diagram shows that the RF channel bandwidth can be up to 20 MHz wide. The RF channel can be divided into 15 kHz sub-channels and bandwidth configuration (allocated sub-carriers) is a portion of the RF channel.
LTE system
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The key parts of a LTE system include:
user equipment (UE), User equipment - can be many types of devices ranging from simple mobile telephones to digital televisions.
evolved node B (eNB), radio access part of the LTE system.
evolved packet core (EPC), uses an IP packet system which can connect to other types of networks such as the public switched telephone network - PSTN through the use of gateway - GW - devices.
LTE system
55
simplified diagram of an LTE system: includes mobile communication devices (user equipment - UE) that can communicate through an evolved node B (eNB), enhanced packet core (EPC) packet switching system.
LTE system is compatible with both the new variable width LTE channels, 5 MHz wide WCDMA radio channels, and narrow 200 kHz GSM channels. This example also shows that the LTE system can provide broadcast video, multimedia (mixed data), and voice services.
LTE evolved Node B (eNB)
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An evolved Node B - eNB - is the radio access part of the LTE system. Each eNB contains at least one radio transmitter, receiver, control section and power supply. In addition to radio transmitters, and receivers, eNBs contain resource management and logic control functionsthat have been traditionally separated into base station controllers (BSCs) or radio network controllers (RNCs). This added capability allows eNBs to directly communicate with each other, eliminating the need for mobile switching systems (MSCs) or controllers (BSCs or RNCs).
LTE evolved Node B (eNB)
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eNB functions include radio resource management - RRM, radio bearer control, radio admission control - access control, connection mobility management, resource scheduling between UEs and eNB radios, header compression, link encryption of user data stream, packet routing of user data towards its destination (usually to EPC or other eNBs), scheduling and transmitting paging messages (incoming calls and connection requests), broadcast information coordination (system information), and measurement reporting (to assist in handover decisions).
Each eNB is composed of an antenna system (typically a radio tower), building, and base station radio equipment. Base station radio equipment consists of RF equipment (transceivers and antenna interface equipment), controllers, and power supplies.
LTE Gateways
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LTE gateways are devices that adapts media transmission between the LTE system and other systems such as the Internet or the public switched telephone network - PSTN.
LTE Gateways
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LTE system uses serving gateways - S-GW and packet gateways - P-GW
A serving gateway, S-GW is a device or assembly that coordinates the control and adapts data transmission between a device and a system. • may adapt communication processes and underlying data to access method
used by device or system with which it is communicating.• also functions as a mobility anchor point (fixed connection route during a
communication session) for handovers between eNBs (inter-eNBhandovers), and an anchor point for inter-3GPP mobility.
A packet gateway is a device or assembly that coordinates the control and adapts packet data transmission between a communication connection and another system. • may adapt data formats and communication processes to the system that it
is communicating with. • may allocate IP addresses or filter packets (deep packet inspection).
LTE Mobile management entity (MME)
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A mobile management entity - MME - is a processing element within the LTE. Can be used to help find, route, and maintain and transfer communication connections to e.g. WiMAX wireless devices.
The MME can perform end to end connection signaling and security services between core networks (Inter CN node signaling). It can perform mode access control to the UE when it is not connected.
The MME can maintain location information about devices and determine which gateway will be used to connect mobile devices to other networks.
LTE Evolved Packet Core (EPC)
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The LTE system uses two basic types of network elements; enhanced node B - eNB base stations and media gateways.
No switch is needed as network elements can communicate with each other to setup connections and connection transfers (handovers).
The LTE system uses an evolved packet core - EPC - to receive, process, and forward packets towards their destinations. The use of an EPC allows for the rapid processing of packets, which increases data throughput while reducing packet delays.
LTE Evolved Packet Core-EPC
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Figure shows the key functional parts of an evolved packet core - EPC - system.
Example shows several types of packet flows (voice, Internet browsing, and video) that are transferred to a user equipment device in a UMTS LTE system.
The serving gateway categorizes each incoming packet and routes it to a mobility tunnel that reaches the eNB (base station). The eNB maps and manages the data transmission to the UE on appropriate radio bearer channels.
LTE network architecture
63
key network elements include • user equipment (UE) • base stations (eNBs)• Evolved Packet Core-EPC• serving gateway (S-GW) and mobile management entity (MME) • subscriber databases (HSS) and packet gateway (P-GW).
UEs communicate with eNBs (base stations) through the Uu radio interface. eNBs can directly communicate with each other using an X2 interface or with MMEs using the S1 interface. MME sets up and manages mobile connections using information from HSS. Calls are controlled by an S-GW and the call or session event information from the S-GW is provided to a policy control and charging function (PCRF) which translates the information into billing records. The S-GW can also link to a serving general packet radio service support node (SGSN) to allow the UMTS system to interoperate with other mobile communication systems including GSM, GPRS, and WCDMA.
LTE network architecture
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The LTE network architecture uses a modular system design called the system architecture evolution -SAE, which is composed of separate components that may be added, removed, or connected together to evolve or improve the capabilities of an existing system.
The LTE system uses an SAE to transition from a voice centric switched network to a universal broadband communications access system.
LTE protocol architecture
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LTE can use use multiple protocols that are divided into processing layers. Each protocol layer performs specific functions. Each protocol layer may also use one or more protocols. The layered approach simplifies for the adding of new functions without requiring significant changes to the system.
Radio resource control - RRC - is a protocol is used to coordinate the operation (control) of the radio.Packet data convergence protocol - PDCP - ensures that all the packets are transferred and placed in correct order. The radio link control - RLC - layer is concerned with maintaining the radio link between the mobile device and the base station. Medium access control layer - MAC - coordinates access requestsand assignment from the system.Broadcast and multicast control - BMC -is responsible for receiving and processing broadcast messages.
LTE protocol layers
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Figure shows how the protocol layers of the LTE system can link the radio device, through the evolved node B (eNB) base station. The LTE radio link is divided into layers where each layer performs its specific function and passes its data on to the next layer above or below.
Physical Layer - The physical layer converts digital bits to and from RF packets that are sent between the UMTS LTE device and the access point.MAC Layer - The medium access control layer (MAC) is the process used to request and coordinate access to the system. RLC Layer - The radio link control layer is concerned with maintaining the radio link between the mobile device and the base station. PDCP Layer - Ensures that all packets are transferred and placed in correct order.
LTE network interfaces
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LTE network interfaces
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This figure shows key LTE network elements and how they interface with each other. LTE network interfaces define the characteristics and processes that are used to connect network elements to each other or to other systems.
Uu Interface - User equipment - UE - communicate with evolved node B (eNB) using the Uu interface.S1 Interface - is used to eNBs to the serving gateway (S-GW).X2 Interface - allows eNBs to directly connect with each other.S6 Interface - allows mobile management entity (MME) to connect with customer database (HSS).S3 Interface - is used to link to existing systems (such as GSM, GPRS, and WCDMA) to the LTE system.S5 Interface - connects the LTE system to packet data networks such as the Internet.S7 Interface - connects the LTE system to operations and support systems.
LTE system operation
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LTE system operates by coordinating connections with mobile devices, managing connection transfers (mobility), setting up and managing service sessions, keeping track of the location of mobile devices, and coordinating the distribution of signals to groups (multicast) or to geographic areas (broadcast).
Connection States - The LTE must identify and control the mode of each wireless device that is operating in its system.Connection Transfers (Mobility) - the LTE system coordinates the transfer of connections as wireless devices move to different radio coverage areas.Session Management (IMS) - The LTE system sets up, initializes, and manages communication services such as voice, data, and video.Location Based Services (LBS) - LTE systems maintain position location information for commercial services, system management, and emergency services.Muticasting and Broadcasting - LTE systems coordinate the distribution of signals to groups of users (multicast) or to geographic regions (broadcast).
LTE mobility states
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Mobility states are the status conditions of a mobile device as it relates to a communication network. Mobility states include detached (unknown), active(communicating), and idle (awaiting actions).This figure that LTE device starts in the detached (unknown status) state when it is turned on. After it registers with the system, it changes into the active state. If the device is inactive for a period of time (does not transfer information), it may be moved into the idle mode. If there is data to be transferred, the mode may be changed back to the active state. When a device is powered off, it informs the system (deregisters) and detaches.
LTE handover (HO)
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LTE Handover is performed by the user equipment devices connecting directly to each other through the eNBs. No switching equipment is required for LTE handovers to other devices in the LTE system.
Can handover within a system (intra-system), to other systems (inter-system), and to systems that use other radio access technologies (Inter-RAT handover).
LTE handover (HO)
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This figure shows the basic handover process that occurs in the LTE system where the system has determined that the signal strength and quality of the radio channel it is receiving and the serving eNB (source eNB) is below desired levels and handover is preferred.
Process starts when the source eNB commands the UE to start measuring the radio channel quality from a nearby base station (target eNB). Using the information from the mobile, it is determined that the adjacent cell site is a candidate for the handover and the direct transfer process starts.
The source eNB informs the target eNB using the X2 interface that a handoff request has been initiated. During the handover process, the source eNB forwards the user data to the target eNB. When the UE has successfully connected to the target eNB, the connection is transferred and the target eNB updates the MME of the transfer completion.
The MME then informs the serving gateway to change the user’s media path (path change) from the source eNB to the target eNB.
IP Multimedia Subsystem (IMS)
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IP Multimedia Subsystem (IMS)
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IP multimedia subsystem - IMS - is set of session based protocols that can be used to provide services using Internet protocol (IP) based. IMS has evolved from its first use in 3rd generation mobile telephone standards that to other types of networks including voice over Internet protocol (VoIP) and IP television (IPTV). IMS can integrate devices and services across multiple types of networks.Set of Session Control Protocols - IMS defines the use of session control protocols (existing and tested protocols such as SIP) to negotiate and initialize protocols that are used for communication sessions.Integrates Systems and Services - The IMS system can be used to integrate different systems and services that can be addressed using IP connetions.
IP Multimedia Subsystem (IMS)
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Started with 3GPP and Evolved to VoIP and IPTV - IMS protocols are so flexible that they have been used in other types of sytsems such as Internet telephony and Internet protocol Television - IPTV.
This figure shows the basic functions of the IMS system. This diagram shows that a user equipment device (a mobile phone in this example) is calling another device (a landline telephone). The UE sends its connection request (an invite) to the proxy call session control function (P-CSCF). The P-CSCF needs to find the call server so it sends a request to the interrogatory call session control sever (I-CSCF). The I-CSCF contacts the home subscriber server (HSS) which contains the service profile of the user and the location of the serving call session control function (S-CSCF). The S-CSCF will then manage the communication session with the UE through the P-CSCF. The IMS system can then connect a call through a media gateway (signaling processes not shown) so the connection can reach the landline telephone.
Location based Services (LBS)
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LTE can provide location information using different types positioning systems including the system itself (network positioning) or through the use of global positioning system - GPS.
Location based Services (LBS)
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LTE location services include:Commercial Location Services (Commercial LCS) - Value added services that are performed using location determination equipment and services such as mapping and advertising.Internal Location Services (Internal LCS) - Position discovery activities and data that are used for network or service operation (find and page the subscriber).Emergency Location Services (Emergency LCS) - Discovery and transfer device location information to emergency facilities or services. Emergency LCS provide agencies with the identification and location of a device that has dialed an emergency services number (such as 112 or 911).
This figure shows how mobile communication systems can use GPS signals to provide location information. A mobile telephone has both mobile communication and GPS reception capability. When the user dials an emergency number, the GPS information can is sent to the public safety access point to allow emergency services to the location of the user’s mobile telephone.Lawful Intercept Location Services (Lawful Intercept LCS) – Provides identification and location information of a device to an authorized public safety agency.
Evolved MBMS
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LTE was designed to allow for shared (multicast) types of services such as digital broadcast radio and digital video broadcast.
The eMBMS feature can simultaneously transmit the same media signals using LTE eNBs to multiple recipients in the same geographic region.
In addition to the shared transmission capability, the two-way capabiltiy of the MBMS system allows users to dynamically interact with the broadcast network. This means that the MBMS system can provide one-way bearer services (multicasting and broadcasting media) and user controlled media streaming.
Evolved MBMS
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This figure shows how the MBMS system can be used to provide radio and television broadcast services. A television station (a or a video subscription channel) is broadcast to all the cells within the LTE system area. Each TV subscription viewer must use a key (previously provided) so they can receive and decode the television signal. A audio broadcast (local radio station) is also connected to some of the LTE cells. Voice broadcast (traffic alerts) are connected to a cells in the system area.
LTE summary
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LTE summary
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LTE was designed to simultaneously provide a mix of servicesranging from real time voice to high-speed Internet browsing.The use of a single IP type of interconnection simplifies deployment, maintenance, and reduces equipment cost.Base stations (eNBs) can directly connect to each other with eliminates the need for a switching system.
The radio structure is flexible (bandwidth, duplex types) which allows LTE to be deployed in different spectrums.IP Multimedia Subsystem - IMS - is used to setup and manage multimedia sessions with devices in and outside of the LTE system.Multiple types of location based services are integrated into the LTE system.
LTE is an evolution of GSM, GPRS, and WCDMA.
LTE ADVANCED
• See SLIDES BY Toskala
• IEEE Tutorial
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Orthogonal frequency-division multiplexing (OFDM)
• method of encoding digital data on multiple carrier frequencies.
• developed into a popular scheme for wideband digital communication, whether wireless or over copper wires, used in applications such as digital television and audio broadcasting, DSL broadband internet access, wireless networks, and 4G mobile communications.
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Orthogonal frequency-division multiplexing (OFDM)
• is a frequency-division multiplexing (FDM) scheme used as a digital multi-carrier modulation method. A large number of closely spaced orthogonal sub-carrier signals are used to carry data. The data is divided into several parallel data streams or channels, one for each sub-carrier. Each sub-carrier is modulated with a conventional modulation scheme (such as quadrature amplitude modulation or phase-shift keying) at a low symbol rate, maintaining total data rates similar to conventional single-carrier modulation schemes in the same bandwidth.
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Orthogonal frequency-division multiplexing (OFDM)
• primary advantage of OFDM over single-carrier schemes is – ability to cope with severe channel conditions (for example,
attenuation of high frequencies in a long copper wire, narrowband interference and frequency-selective fading due to multipath) without complex equalization filters.
– low symbol rate makes use of a guard interval between symbols affordable, making it possible to eliminate intersymbol interference (ISI) and utilize echoes and time-spreading (that shows up as ghosting on analogue TV) to achieve a diversity gain, i.e. a signal-to-noise ratio improvement. This mechanism also facilitates the design of single frequency networks (SFNs), where several adjacent transmitters send the same signal simultaneously at the same frequency, as the signals from multiple distant transmitters may be combined constructively, rather than interfering as would typically occur in a traditional single-carrier system.
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Supplementary slides based on ieee tutorial
