Broadband Wireless Access – Standards
In this unit, Jürgen Kock tells us about the broadband wireless access standards, why do we need technical standards, who defines BWA standards, WiMAX standards and long term evolution.
Why do we need technical standards?
Standards define key aspects of a technology. Thanks to standardization consumers can for example buy any kind of AA battery and be sure, that it’ll work in most, if not all, devices that specify the use of this kind of batteries. While batteries follow global standards, power plugs are only defined on a national basis. Travelers know about this inconvenience.
In wireless communication, standards ensure interoperability between user devices and the radio network of different vendors. Frequency bands, modulation techniques, power levels and encryption are just some of the aspects covered by standards.
Who defines BWA standards?
The ITU-R (International Telecommunication Union – Radiocommunication Sector) started in the 1980s to define the requirements for a 3rd generation of mobile communication systems. As an agency of the UN (United Nations) the ITU combines the effort of governments and the telecommunication industries for a worldwide supported standardization. Finally, in the year 2000 the ITU approved the technical specifications for the 3rd generation of mobile networks under the name "IMT-2000" (International Mobile Telecommunications-2000). One goal of IMT-2000 is to provide seamless delivery of services. The minimum requirements for data speed were defined at 2Mbps for stationary or walking users and 348 kbpsfor fast moving users in vehicles.
The ITU has coined the term IMT Advanced to identify mobile systems whose capabilities go beyond those of IMT 2000. In order to meet this new challenge, 3GPPs Organizational Partners have agreed to widen 3GPP’s scope to include the development of systems beyond 3G.
Some of the key features of IMT-Advanced will be:
Enhanced peak data rates to support advanced services and applications (100 Mbit/s for high and 1 Gbit/s for low mobility) Source: http://bit.ly/qYLvQj
Two competing technologies are the basis for Broadband Wireless Access. The evolution of mobile or cellular networks called Long Term Evolution (LTE)lies under the responsibility of the ITU and the 3GPP (3rd Generation Partnership Program). We’ll start our discussion with the competing technology called WiMAX (Worldwide Interoperability for Microwave Access).
WiMAX is based on the IEEE suite of standards 802.16. The initial standard was released in 2001 and is named 802.16-2001 accordingly. The goal was to define a wireless broadband technology for fixed users, with a range of up to 50 km and data rates that can compete with wireline DSL (Digital Subscriber Line). For achieving coverage of such wide distances, this initial standard required a line-of-sight between sender and receiver, which was soon seen as a limitation of the technology.
In 2004 the standard was updated, but still covered only fixed users. 802.16d-2004 is therefore referred to as the current standard for Fixed WiMAX. The frequency range 2 – 11 GHz’s was added to the previously defined range of 10 – 66 GHz’s. The new range allowed for static connections without a line of sight. Static means, that there is no handover mechanism defined, when a user moves out of the range of his cell.
With 802.16e-2005 the standards where extended to cover Mobile WiMAX. Handover and roaming support was added for slow moving users. The frequency bands used for mobile users are 2.3 and 2.5 GHz. Of course, service providers can also offer fixed access in those frequencies.
The latest release of the WiMAX standards 802.16m-2011 defines an advanced air interface with data rates of up 1 gigabit. This fulfills the formal requirements of 4G networks as defined by the ITU.
LTE – Long Term Evolution
LTE is defined by the 3GPP (3rd Generation Partnership), a collaboration between groups of telecommunications associations. It provides detailed technical specifications to cover all aspects of a cellular communication network within the frameworks IMT-2000 and IMT Advanced of the ITU.
The standardization is published in so called Releases. Release 1 to 7 covered 2G and 3G networks including UMTS (Universal Mobile Telecommunications System).
Source: Anritsu, Understanding LTE (http://bit.ly/NDBlKf)
Release 8, published in 2008, marked the first LTE standard. The goal of 3GPP was to define an evolutionary upgrade of cellular networks, providing higher data rates and improved quality of service. At the same time the demand for cost reduction and a low complexity of the network architecture was addressed. Unlike the WiMAX standard, LTE standardization encompasses the whole network architecture including the radio network, core network and service architecture.
Here is an overview of the key requirements and features of the different 3GPP LTE releases:
- Optimized for low mobile speed from 0 to 15 km/h.
- Higher mobile speed between 15 and 120 km/h should be supported with high performance.
- Mobility across the cellular network shall be maintained at speeds from 120 km/h to 350 km/h (or evenup to 500 km/h depending on the frequency band).
- Throughout, spectrum efficiency and mobility targets above should be met for 5 km cells, and with aslight degradation for 30 km cells.
Release 8 - 2008
This was the first LTE release. The release contains 36 technical specifications.
- Evolved radio access
- New air interface (not backward compatible)
- High spectral efficiency
— OFDM (Orthogonal Frequency Division Multiple Access) in Downlink, Robust against multipath interference (reduces path loss)
— Single-Carrier FDMA in Uplink
- Variable bandwidth: 1.4, 3, 5, 10, 15 and 20 MHz
- Support of Multiple Antenna technology MIMO
- FDD and TDD within a single radio access technology
- Simple Architecture
- Very low latency: Short setup time and short transfer delay
- Evolved Packet Core
- Reduced complexityof the core network
- All IP network SAE (System Architecture Evolution)
- Support of Self-Organizing Network (SON) operation
Source: LTE-Release 8 User Equipment Categories, http://bit.ly/9R0DIm
Release 9 - 2009
Release 9 brings enhancements and Improvements for
- System Architecture Evolution
- WiMAX and LTE/UMTS Interoperability
- Location services
- Emergency services
- Broadcast services
- Voice Over LTE (VoLTE)
Release 10 – 2011 - LTE-Advanced
- First release of LTE Advanced
- Backwards compatible with release 8 (LTE).
- Fulfilling IMT Advanced 4G requirements (For example 1 Gbps peak downlink data rate)
- Multi-Cell HSDPA with 4 carriers
Release 11 – planned in 2012 Q3
- Advanced IP Interconnection of Services
- Service layer interconnection between national operators/carriers as well as third party application providers
Peak Data Rates
Sources – Further Readings:
- ITU Overview for IMT-2000 (http://bit.ly/NdSM8E)
- ITU Entry Point for IMT Advanced (http://bit.ly/f5FqtH)
- Homepage of 3GPP (http://bit.ly/Cai9O)
- 3GPP Entry Point forLTE (http://bit.ly/Cai9O)
- 3GPP Entry Point for LTE Advanced (http://bit.ly/Cai9O)
- Wikipedia article about 3GPP (http://bit.ly/dugu8O)
- 3GPP technical paper UTRA-UTRAN Long Term Evolution (LTE) and 3GPP System Architecture Evolution (SAE) including high level requirements (http://bit.ly/NhbfeE)
- E-Learning on LTE and other Telecommunication Fundamentals (http://bit.ly/NdTd2A)
- LTE Introduction (http://bit.ly/rxQDzE)