Wireless access standards for NGN

IMT-2000 is the global standard for third generation (3G) wireless communications, defined by a set of interdependent ITU Recommendations. It provides a framework for worldwide wireless access by linking the diverse systems of terrestrial and/or satellite based networks.

On the other hand, the IEEE has developed standard 802.16, designed specially for wireless Metropolitan Area Networks (MAN) outdoor applications. IEEE 802.16, Air Interface for Fixed and Mobile Broadband Wireless Access Systems, nicknamed “WiMAX” allows for delivering broadband speeds over wireless networks. Considering that networks are moving towards packet-based services and are becoming IP centric and worldwide convergence is taking place in which wireless medium plays a critical role, it is recommended that the PCC.I WG on Technology considers studying wireless access standards for Next Generation Networks.

Introduction

The main areas of ITU standards activities on IMT-2000 are distributed in Telecommunications Standardization (ITU-T), the Radiocommunication (ITU-R) and the Telecommunications Development (ITU-D) Sectors. The ITU-T Study Group 19 "Mobile Telecommunication Networks" is responsible for studies related to network aspects of mobile telecommunications networks, including International Mobile Telecommunications 2000 (IMT-2000) and beyond, wireless Internet, convergence of mobile and fixed networks, mobility management, mobile multimedia functions, internetworking, interoperability and enhancements to existing ITU-T Recommendations on IMT-2000.

In order to obtain Global Roaming, the IMT-2000 project formed two groups for the standardization of terrestrial networks: 1) 3GPP (3rd Generation Partnership Project) to develop the evolution of the Global System for Mobile Communications (GSM) towards the Universal Mobile Telecommunications System (UMTS) and 2) 3GPP2 to develop the evolution of the Interim Standard 95 (IS-95) towards the Code Division Multiplex Access 2000 (CDMA 2000). Another wireless access standard is IEEE.802.16, nicknamed WiMAX and also called now “World Interoperability for Microwave Access”. This standard enables broadband speeds over wireless networks. The ITU-R has recently approved Recommendation F.1763 on "Radio interface standards for broadband wireless access systems in the fixed service operating below 66 GHz" which recommends IEEE Std 802.16-2004.

Discussion IMT-2000 Standards

3GPP

The 3GPP is an organization formed by several partners. These are: the Association of Radio Industries and Businesses (ARIB) and the Telecommunication Technology Committee (TTC) of Japan; the European Telecommunications Standards Institute (ETSI); the Alliance for Telecommunications Industry Solutions (ATIS) of USA and the Telecommunications Technology Association (TTA) of Korea.

As mentioned above, 3GPP is developing the evolution of GSM towards UMTS.

GSM uses Time Division Multiplexing (TDMA) to allocate the different voice and signaling channels and it has digital call quality on both types of channels, which means that it is considered a second generation (2G) mobile phone system. GSM is an open standard developed by the 3rd Generation Partnership Project (3GPP). Most GSM networks operate in the 900 MHz or 1800 MHz bands.

UMTS represents an evolution in terms of capacity, data speeds and new service capabilities from second generation mobile networks. UMTS is a key member of the global family of third generation (3G) mobile technologies. 3G/UMTS offers mobile operators significant capacity and broadband capabilities to support greater number of voice and data customers plus higher data rates at lower incremental cost than 2G.

3G/UMTS has been specified as an integrated solution for mobile voice and data with wide area coverage. 3G/UMTS uses WCDMA (Wideband Code Division Multiple Access) as the radio access technology. This technology is based on a radio technique with a wideband spread-spectrum proposed by ETSI Alpha group and its specification was finalized in 1999.While using an automatic international roaming, 3G/UMTS ads integral security and billing functions, allowing operators to migrate easily from 2G to 3G.

3GPP2

GPP2 is also an organization formed by several partners. They are: the Telecommunications Industry Association (TIA) of US, the ARIB/TTC of Japan, the TTA of Korea and the China Wireless Telecommunication Standard Group (CWTS). As also mentioned before, 3GPP2 is developing the evolution of IS-95 towards CDMA 2000.

IS-95 (Interim Standard 95) is the first Code Division Multiplex Access (CDMA) based digital cellular standard pioneered by Qualcomm. IS-95 is also known as TIA-EIA-95. [3] It is a 2G mobile telecommunications standard that uses CDMA a multiple access scheme for digital radio to send voice, data and signaling data (such as a dialed telephone number) between mobile phones and cell sites. The transmission is done in streams of bits. CDMA permits several radios to share the same frequencies and unlike TDMA (Time Division Multiple Access), a competing system used in GSM, all radios can be active all the time, because network capacity does not directly limit the number of active radios. Since larger numbers of phones can be served by smaller numbers of cell-sites, CDMA-based standards have a significant economic advantage over TDMA-based standards, or the oldest cellular standards that used frequency division multiplexing. IS-95 is now being supplanted by IS-2000 (CDMA2000), a later CDMA-based standard. It is used in the USA, South Korea, Canada, Mexico, India, Israel, Australia, Venezuela and China. CDMA2000 has already been implemented to several networks and is fully backwards compatible with IS-95B. CDMA2000 is not constrained to only the IMT-2000 band, but operators can also overlay a CDMA2000 1x system, which supports 144 kbps now and data rates up to 307 kbps in the future, on top of their existing previous versions of CDMA networks.

The evolution of CDMA2000 1x is labeled CDMA2000 1xEV. 1xEV will be implemented in steps: 1xEV-DO and 1xEV-DV. 1xEV-DO stands for "1x Evolution Data Only". 1xEV-DV stands for "1x Evolution Data and Voice". Both 1xEV CDMA2000 evolution steps will use a standard 1.25 MHz carrier. 1xEV-DO probably will be available for CDMA2000 operators during 2002 and 1xEV-DV solutions will be available approximately late 2003 or early 2004.

CDMA2000 1x EV-DO and CDMA2000 3x are ITU-approved, IMT-2000 (3G) standards. CDMA2000 3x is part of what the ITU has termed IMT-2000 CDMA MC (Multi Carrier). It uses less that 5 MHz spectrum (3x 1.25 MHz channels) to give speeds of over 2 Mbps. CDMA2000 1x with lower data speed is considered to be a 2.5G technology.

3GPP updates a new release of the UMTS standard almost each year, the first one was R99 and then there were: Rel4, Rel 5, Rel 6 and now is currently working on Rel 7.

ITU-T Recommendation Q.1741.4 “IMT-2000 References to Release 6 of GSM evolved UMTS Core Network” was prepared by ITU-T SG 19 but uses parts of the 3GPP organization standards.

The Core Network for this IMT-2000 family member referred to as “3GPP Release 6” is based on evolved Core Network from the 3rd generation release 1999. This core network supports both 2nd and 3rd generation radio access networks as options. This Recommendation identifies a release of the IMT-2000 Family Member, “GSM evolved UMTS Core Network”. This release of the Family Member is known to the Standards Development Organizations (i.e., ARIB, CCSA, ETSI, ATIS, TTA, and TTC) as the “3GPP Release 6”. Earlier releases, known as “3GPP Release 99”, “3GPP Release 4”, and “3GPP Release 5”, of this Family Member are specified in the Recommendation Q.1741.1, Q.1741.2, and Q.1741.3, respectively, while other IMT-2000 Family Members are specified in other Recommendations in the Q.174x series.

Previous versions of this Recommendation were called “GSM evolved UMTS Core Network with UTRAN Access Network” where UTRAN stands for UMTS Terrestrial Radio Access Network.

UTRAN is a wireless access network that can carry many traffic types including Circuit Switched and IP Packet Switched data flows. UTRAN allows connectivity between the UE (user equipment) and the core network. As explained above, UMTS uses code division multiple access (CDMA).

The UTRAN contains the base stations, which are called Node Bs and Radio Network Controllers (RNC). Nodes Bs are base transceiver stations which uses WCDMA as air transport technology. The RNC provides control functionalities for one or more Node Bs. A Node B and an RNC can be the same device, although typical implementations have a separate RNC located in a central office serving multiple Node B's. Despite the fact that they do not have to be physically separated, there is a logical interface between them known as the Iub. The RNC and its corresponding Node Bs are called the Radio Network Subsystem (RNS). There can be more than one RNS present in an UTRAN. ITU-T Draft new Recommendation Q.1742.5: IMT-2000 References to ANSI-41 evolved Core Network with cdma2000 Access Network has been submitted for consent by ITU-T SG 19 in July 2006. This Recommendation identifies the IMT-2000 Family Member; “ANSI-41 evolved Core Network with cdma2000 Access Network.” This set of referenced specifications includes those 3GPP2 specifications that were approved as of 31 December 2005.

The Core Network interfaces identified in this recommendation and the radio interfaces and radio access network interfaces identified in ITU-R Recommendation M.1457, Specifications of the radio interfaces of International Mobile Telecommunications-2000 (IMT-2000), constitute a complete system specification for the 3rd generation mobile system for terrestrial usage of this IMT-2000 Family Member. In the event that a referenced specification also includes material that specifies any of the radio aspects of this IMT-2000 family member, ITU-R Recommendation M.1457, shall take precedence.

IEEE 802.16e “WiMAX”

There is a tremendous growth in wireless applications and services and the world is witnessing increasing demand for multimedia and broadband applications. Networks are moving towards packet-based services and are becoming IP centric and worldwide convergence is taking place in which wireless medium plays a critical role. In this respect the boundaries between 3G and Broadband Wireless Access (BWA) are rapidly being blurred and that these solutions can complement each other very effectively.

The IEEE 802.16e Task Group (Mobile WirelessMan) released on February 2006 its standard “Air Interface for Fixed and Mobile Broadband Wireless Access Systems Amendment for Physical and Medium Access Control Layers for Combined Fixed and Mobile Operation in Licensed Bands”.

The first IEEE 802.16 standard was approved in December 2001 and was followed by three amendments – 802.16a, 802.16b and 802.16c to address issues of radio spectrum, quality of service and inter-operability, respectively. Another amendment, 802.16e addressing mobility was finalized in 2005. Although the 802.16 family of standards is officially called WirelessMAN, it has been dubbed WiMAX by an industry group called The WiMax Forum. The mission of the Forum is to promote and certify compatibility and interoperability of broadband wireless products. Now the acronym WiMAX expands to "Worldwide Interoperability for Microwave Access".

WiMAX is a wireless broadband technology, which supports point to multi-point (PMP) broadband wireless access over long distances with high throughput. WiMAX works in a very different way than Wi-Fi (IEEE Wireless LAN standard 802.11). WiFi uses contention access through its Media Access Controller (MAC), meaning that all subscriber stations compete for access points on a random basis, which can cause that distant nodes maybe interrupted more than closer nodes, reducing their throughput and for that not very suitable for services such as VoIP, IPTV, etc. WiMAX instead, uses a scheduling MAC, meaning that subscriber stations only compete once for the initial entry into the network. Once they enter, they are allocated a time slot by the base station. This time slot is not always the same length but it remains assigned to the subscriber station, not being able to be used by others. The scheduling mechanism allows the base station to control the Quality of Service (QoS).

The ITU-R approved on April 2006 Recommendation ITU-R F.1763 on "Radio interface standards for broadband wireless access systems in the fixed service operating below 66 GHz." This standard, developed by WP9B in SG9, recommends IEEE Std 802.16-2004 as well as the compatible ETSI BRAN HIPERMAN standard.

Proposal

Wireless access technologies are widely used by almost everyone in the world. The Next Generation Networks are pursuing seamless convergence between fixed and wireless communications. It is recommended that the Working Group on Technology considers studying wireless access standards for Next Generation Networks.

Oscar Avellaneda
Chair
Working Group on Technology
PCC.I
e.mail: avellaneda.oscar@ic.gc.ca