UMTS: The Next Ten Years
UMTS: The Next Ten Years - January, 2008
High Speed Downlink Packet Access (HSDPA) and similar enhancements to the uplink have the potential to take UMTS beyond the target capabilities of 3G. But did you know that 3GPP has already started work on how UMTS radio access will evolve towards, through, and even beyond, 4G?
This project is known as Long Term Evolution (LTE) and its aim is the development of the radio access network that will eventually supersede UMTS. This includes a completely new air interface and a new radio access network architecture. A general description of the aims for LTE are set out in the 3GPP document 25.913. The overall goals are summarized here and they represent a significant step up in capability while at the same time reducing CAPEX and OPEX:
- significantly increased peak data rate: downlink 100 Mbit/s, uplink 50 Mbit/s
- increased cell edge bit rate for more consistent service level
- significantly improved spectrum efficiency; 2–4 times that of Rel-6
- reduced latency to below 10 ms
- transition time from the idle state to an active state in less than 100 ms
- transition time from a dormant state to an active state in less than 50 ms
- scalable bandwidth: 1.25, 1.6, 2.5, 5, 10, 15 or 20 MHz
- optimized for interworking with an enhanced IMS and core network
- efficient support of packet-based services
- optimized for both low and high terminal speeds
- cost-effective migration from Rel-6
- acceptable terminal complexity, cost and power consumption
- backward compatibility
- interworking with non-3GPP technologies
- enhanced Multimedia Broadcast and Multicast Service (MBMS)
At the heart of LTE is a new air interface, which is based on a combination of OFDMA (downlink) and SC-FDMA (uplink). This combination of multiple access technologies brings great flexibility, scalability and spectral efficiency. It is designed to support varying degrees of quality of service along with very high potential bit rates in both downlink and uplink directions. It is clear that the radio link will need to offer a smooth transition and almost certain coexistence with the current UMTS air interface. It is likely that terminals will need multi-RAT capabilities at least to support GSM/GPRS, UMTS and E-UTRA. There may also be considerable impetus to support non-3GPP radio access techniques such as WiFi, 1xEV or WiMAX.
The new air interface is supported on a new radio access network known as E-UTRAN. E-UTRAN architecture is very different to that of today's UTRAN. It is built entirely on an IP-based transmission network and has a much more distributed functional architecture. In fact, the RNC concept is removed completely and both the radio resource control and the link control functionality are implemented in the new LTE base stations, which are known as eNode Bs.
The services will be a mixture of real-time, non-real-time and broadcast requiring carefully devised QoS mechanisms that can deal with service provision on an end-to-end basis. LTE is defined in the 3GPP 36-series documents and Wray Castle already offers a one-day technical overview introducing the key new concepts appearing in this LTE documentation.
We will be keeping a close eye on all these developments and there will be even more detailed training available when you need it.
© Wray Castle Limited January 2008