The work focused on the decision of the radio technology as well as the system architecture. It concluded that needed something new and not just an extension of the WCDMA system as a result of a complex set of requirements to cover different bandwidths and a certain amount of data transfer rates.
© 2010 PontoTech
45
Groups) which are listed under each group of technical specifications (TSG, Technical Specifications Group). This distribution is shown in the next figure.
Figure 16 - Work structure of the 3GPP
As part of the main specifications for the access network, it was decided to use technology Multiple Access Orthogonal Frequency Division (OFDMA, Orthogonal Frequency Division Multiple Access) as technology in the downlink. To access uplink technology was chosen Division Multiple Access Single Carrier Frequency (SC-FDMA Single Carrier Frequency Division Multiple Access) as the most favorable, a decision that was supported by manufacturers and operators in general. A significant improvement over WCDMA is the technology that both Frequency Division Duplexing (FDD, Frequency Division Duplexing) such as Time Division Duplexing (TDD, Time Division Duplexing) have the same solution for multiple access, ie that an adjustment is made to minimize the differences in their modes of operation. This decision by the multiple access was made official in 2005 and after that the work was focused on the technologies chosen for LTE.
Also, it was decided that it should have a radio access network (RAN, Radio Access Network) of a single node, which is achieved by putting all the functionality of the radio base station (Node B). The name of this new element is eNodeB, representing the letter "e", evolved. The main difference in relation to this aspect is that it removes the element RNC delegating its functions to the eNodeBs.
The specifications for the evolved packet core (EPC Evolved Packet Core) are covered by the technical specification group core network and terminals (TSG CT, Technical Specification Group Core and Terminals) and also by the group of
technical specifications services and systems (TSG SA, Technical Specification Group Services and System Aspects). The group of technical specifications of the radio access network GSM / EDGE (GERAN TSG, Technical Specification Group GSM / EDGE Radio Access Network) is responsible for changes in GSM / EDGE introduced in Release 8 to facilitate interoperability between LTE and GERAN. For its part the group of technical specifications of the radio access network WCDMA (TSG RAN, Technical Specification Group Radio Access Network) is responsible for the changes introduced in WCDMA Release 8 to facilitate interoperability between LTE and WCDMA.
4.3 3GPP requirements for LTE
In November 2004, began work related to the evolution of the access network known as UTRAN. In this work were present operators, manufacturers and research
institutes with a large number of proposals and views.
Then, in early 2005 began work on the specification of 3GPP LTE, which published its technical report TR 25.913, Requirements for Evolved UTRA (E-UTRA) and Evolved UTRAN (E-UTRAN). After that recent versions have been published with improvements and fixes, version 9.0.0 being the last one.
Key elements of this technical report are described below.
4.3.1 Requirements related to the ability
• Data transfer rates: E-UTRA should support significant increases in data transfer rates, which must be consistent with the spectrum allocation and terminal configuration. For example, a terminal to be able to support maximum speeds of 100 Mbps in the downlink (DL, downlink) and 50 Mbps in the uplink (UL, uplink), each with an allocation of 20 MHz spectrum.
• Latency: In the control plane must have a latency equal to or less than 50 milliseconds (ms) between active and inactive states. For the user plane must have a latency no greater than 5ms for a one-way transmission from the transmitted packet is available at the IP layer at the edge of the border UE / RAN until it becomes available in the IP layer the other border RAN / EU.
© 2010 PontoTech
47
4.3.2 Requirements related to performance
• Transfer Rate: Transfer rate (throughput) in the downlink (DL) should be for the average user, 3 to 4 times compared to the specifications assigned to HSDPA Release 6, using more than two transmission antennas in the base station and two receive antennas in the terminal device. Besides the transfer fee should be scalable in line with the allocation of spectrum. For the uplink (UL) should have a transfer rate per user on average 2 to 3 times as specified in Release 6, in this case using a transmitting antenna in the terminal and two receiving antennas at the base station. It should get a higher data rate using multiple transmit antennas in the terminal device.
• Spectral Efficiency: Spectral efficiency (bps / Hz / site) in the downlink (DL) should be 3 to 4 times that obtained with a system based on Release 6 HSDPA, using two transmission antennas in the base station and two
reception terminal. In the uplink (UL) should be 2 to 3 times Release 6 HSDPA obtained and E-UTRA using a transmitting antenna in the terminal and two reception at the base station.
• Mobility: Must be optimal for the user transfer rates in the range of 0 km / h 15 km / h. For speeds of 15 km / h and 120 km / h mobility must be supported with high performance. For its part, the mobility across the cellular network must be maintained at speeds of 120 km / h 350 km / h, or 500 km / h
depending on the frequency band used (An example of this scenario would be within high speed train). Services real-time voice and supported in the domain of circuit-switched network UTRAN (Release 6) should be borne by the E-UTRAN in the packet switched domain to a higher quality or at least equal.
• Coverage: coverage up to 5 km in the range of cells must meet the requirements of transfer rate (throughput), spectral efficiency and mobility above. In a range of up to 30 km degradations accepted transfer rates and spectrum efficiency, but must comply fully with the requirements of mobility.
For greater ranges requirements have not been defined.
• Enhanced MBMS (Multimedia Broadcast and Multicast Service), MBMS service is a feature you are looking for an efficient way to deliver broadcast and multicast services over the network core. E-UTRA should support
enhanced modes of UTRA MBMS in comparison with less downtime, provided they are caused by the E-UTRAN network.
• Network Synchronization: It is expected that the requirements described in the technical report TR 25.913 are made in the deployment of the network without the use of synchronization between sites.
4.3.3 Requirements related to network deployment
• Deployment scenarios: There is a wide range of deployment scenarios that can be considered, however at a high level, E-UTRAN should be able to support basically two different scenarios. The first is the deployment of E-UTRAN network as an independent network, where the operator deploys the network without the existence of other networks in the area or there are other networks UTRAN / GERAN, or where there is no need for interoperability between them. The second deployment scenario corresponds to a UTRAN network integration and / or networks of GSM EDGE Radio Access (GERAN, GSM EDGE Radio Access Network). In this case the network operator has to totally cover the same geographical area. The deployment and the associated requirements will be defined by demand for mobile services and the
environment of competition between operators.
• Spectral Flexibility: Must support spectrum allocations of different sizes, which means you should be able to operate in a bandwidth of 1.4 MHz, 3 MHz, 5 MHz, 10 MHz, 15 MHz and 20 MHz for uplink and in the downward. It should also be flexible enough to support transmissions in both directions (DL & UL) making optimal use of available spectrum.
• Deployment in the radio spectrum: E-UTRA should be capable of withstanding the following scenarios.
o GERAN/3G coexistence with adjacent channel
o Coexistence between operators on adjacent channels
o Coexisting with spectrum sharing and / or adjacent to the borders of countries
o Operating as an independent network, ie without other networks operating in the same geographic area
• Coexistence and interoperability with other radio access technologies 3GPP (3GPP RAT Radio Access Technology): Terminals UTRAN LTE will also support and / or GERAN should be able to perform handovers to and from E-UTRAN networks. Disruption of services in real time during a handover
between E-UTRAN network and a UTRAN should be less than 300 ms and for services that are not in real time should not exceed 500ms. For handovers between E-UTRAN and GERAN should meet the same requirements of time in both cases.
© 2010 PontoTech
49
4.3.4 Requirements for E-UTRAN architecture
E-UTRAN should have a single architecture based on packet switching, not ceasing to be capable of supporting real-time services based on circuit switched domain. It should also support quality of service (QoS, Quality of Service) point to point, taking into consideration the different types of traffic. Finally, the E-UTRAN should be designed so as to minimize delay variations (jitter) for packet TCP / IP.
4.3.5 Requirements for radio resource management
• Improved support for quality of service point to point: E-UTRAN should be able to support improved control over the quality of service, providing a better matching of service requirements, protocols and applications with the resources and network features access.
• Efficient transmission of higher layers: You must provide mechanisms for the transmission and operation of higher layer protocols on the radio interface.
• Support of load sharing and policy management across different radio access technologies (RAT): This aims to reduce latency and ensure quality of service point to point, when there are different body handovers radio access
technologies.
4.3.6 Requirements related to the complexity of the systems
• Complexity of the system in general: Significantly reduce the complexity of the system to stabilize the interoperability in early stages and further reduce costs in terminals and the network itself.
• Complexity of terminal: The requirements of E-UTRA and E-UTRAN should be possible to reduce the complexity of terminal equipment in terms of size, weight and battery life among others, always consistent with the advanced network services.
4.3.7 Protocols and services requirements
The architecture should enable optimization of communication protocols in addition to reducing the cost of future network deployments. On the other hand all the interfaces should be open to ensure interoperability among equipment manufacturers.
E-UTRA should efficiently support various types of services such as web browsing, video streaming or voice over IP (VoIP) and more advanced services such as real time video. The VoIP service should be supported with at least the same features as the voice service over UMTS networks based on circuit switching.
4.3.8 Specifications for interoperability with legacy networks
One of the requirements of the new system is to ensure interoperability with 3GPP systems Rel.6, ie SAE expected to coexist with the 3GPP mobile communication networks today. In this way, users can establish a data session in a LTE area where coverage is insufficient, and continuing it in a transparent manner with UMTS,
minimizing packet loss and downtime.
Another notable design premise of this new architecture is that not only must ensure interoperability with 3GPP legacy systems of second and third generation, but also must provide seamless mobility and continuity of user session between 3GPP accesses and not "3GPP”, such as WiFi or WiMAX.
To handle mobility between 3GPP access and non-3GPP has chosen to use mobility skills defined by the IETF (Internet Engineering Task Force), such as Mobile-IP and Proxy Mobile-IP in the SAE GW acts as an anchor point. This involves defining a new interface between the SAE GW S2 and non-3GPP accesses and the requirement that interfaces S5 and S8 (discussed below) support simultaneous GTP protocol (3GPP accesses) and IETF-based protocols (non-3GPP access) depending on the type of access.
Therefore, it was proposed an evolution of the architecture according to the 3GPP standard deliveries (next figure).
© 2010 PontoTech
51
Figure 17 - Evolution of 3GPP was a flatter architecture