LTE
LTE (both radio and core network evolution) is now on the market. Release 8 was frozen in December 2008 and this has been the basis for the first wave of LTE equipment. LTE specifications are very stable, with the added benefit of small enhancements being introduced in Release 9, a Release that will be functionally frozen in December 2009.
Motivation for 3GPP Release 8 – The LTE Release
- Need to ensure the continuity of competitiveness of the 3G system for the future
- User demand for higher data rates and quality of service
- Packet Switch optimised system
- Continued demand for cost reduction (CAPEX and OPEX)
- Low complexity
- Avoid unnecessary fragmentation of technologies for paired and unpaired band operation
LTE Release 8 Key Features
- High spectral efficiency
— OFDM in Downlink, Robust against multipath interference & High affinity to advanced techniques such as Frequency domain channel-dependent scheduling & MIMO
— DFTS-OFDM(“Single-Carrier FDMA”) in Uplink, Low PAPR, User orthogonality in frequency domain
— Multi-antenna application - Very low latency
— Short setup time & Short transfer delay
— Short HO latency and interruption time; Short TTI, RRC procedure, Simple RRC states - Support of variable bandwidth
— 1.4, 3, 5, 10, 15 and 20 MHz - Simple protocol architecture
— Shared channel based
— PS mode only with VoIP capability - Simple Architecture
— eNodeB as the only E-UTRAN node
— Smaller number of RAN interfaces, eNodeB « MME/SAE-Gateway (S1), eNodeB « eNodeB (X2) - Compatibility and inter-working with earlier 3GPP Releases
- Inter-working with other systems, e.g. cdma2000
- FDD and TDD within a single radio access technology
- Efficient Multicast/Broadcast
— Single frequency network by OFDM - Support of Self-Organising Network (SON) operation
LTE Release 8 Major Parameters
LTE-Release 8 User Equipment Categories
LTE Release 8 Specifications
- LTE is specified in 36 series technical specifications
- The latest version of the LTE Release 8 specifications (September 2009 version) can be found in On-line in the 36 series
LTE Historical Information
The technical paper UTRA-UTRAN Long Term Evolution (LTE) and 3GPP System Architecture Evolution (SAE) is a good starting point.
Initiated in 2004, the Long Term Evolution (LTE) project focused on enhancing the Universal Terrestrial Radio Access (UTRA) and optimizing 3GPP’s radio access architecture.
Targets were to have average user throughput of three- to four-times the Release 6 HSDPA levels in the Downlink (100Mbps), and two to three times the HSUPA levels in the Uplink (50Mbps).
In 2007, the LTE of the 3rd generation radio access technology – “E UTRA” – progressed from the feasibility study stage to the first issue of approved Technical Specifications. By the end of 2008, the specifications were sufficiently stable for commercial implementation.
Orthogonal Frequency Division Multiplexing (OFDM) was selected for the Downlink and Single Carrier-Frequency Division Multiple Access (SC-FDMA) for the Uplink. The Downlink supporting data modulation schemes QPSK, 16QAM, and 64QAM and the Uplink BPSK, QPSK, 8PSK and 16QAM.
LTE’s E UTRA uses a number of defined channel bandwidths between 1.25 and 20 MHz (contrasted with UTRA’s fixed 5 MHz channels).
4 x Increased Spectral Efficiency, 10 x Users Per Cell
Spectral efficiency is increased by up to four-fold compared with UTRA, and improvements in architecture and signalling reduce round-trip latency. Multiple Input / Multiple Output (MIMO) antenna technology should enable 10 times as many users per cell as 3GPP’s original W CDMA radio access technology.
To suit as many frequency band allocation arrangements as possible, both paired (FDD) and unpaired (TDD) band operation is supported. LTE can co-exist with earlier 3GPP radio technologies, even in adjacent channels, and calls can be handed over to and from all 3GPP’s previous radio access technologies.
In the same time frame as the development of LTE, 3GPP’s core network has been undergoing System Architecture Evolution (SAE), optimizing it for packet mode and in particular for the IP-Multimedia Subsystem (IMS) which supports all access technologies.
